Declines in American Adults’ Religious Participation and Beliefs, 1972-2014

Previous research found declines in Americans’ religious affiliation but few changes in religious beliefs and practices. By 2014, however, markedly fewer Americans participated in religious activities or embraced religious beliefs, with especially striking declines between 2006 and 2014 and among 18- to 29-year-olds in data from the nationally representative General Social Survey (N = 58,893, 1972-2014). In recent years, fewer Americans prayed, believed in God, took the Bible literally, attended religious services, identified as religious, affiliated with a religion, or had confidence in religious institutions. Only slightly more identified as spiritual since 1998, and then only those above age 30. Nearly a third of Millennials were secular not merely in religious affiliation but also in belief in God, religiosity, and religious service attendance, many more than Boomers and Generation X’ers at the same age. Eight times more 18- to 29-year-olds never prayed in 2014 versus the early 1980s. However, Americans have become slightly more likely to believe in an afterlife. In hierarchical linear modeling analyses, the decline in religious commitment was primarily due to time period rather than generation/birth cohort, with the decline in public religious practice larger (d = −.50) and beginning sooner (early 1990s) than the smaller (d = −.18) decline in private religious practice and belief (primarily after 2006). Differences in religious commitment due to gender, race, education, and region grew larger, suggesting a more religiously polarized nation.

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Article
Are Americans less religious than they used to be? In previous research, the answer depended on how religious commitment was measured. Most studies agree that religious affiliation has declined in the United States since the 1970s; for example, more Americans in recent years chose "none" when asked to identify their religion (e.g., Hout & Fischer, 2002;Lim, MacGregor, & Putnam, 2010;Pew Research Center, 2015). However, several recent studies have concluded that religious service attendance, belief in God, and prayer have not changed or have even increased in recent years (e.g., Dougherty, Johnson, & Polson, 2007;Presser & Chaves, 2007;Smith & Snell, 2009;P. Taylor, 2014;Wachholtz & Sambamoorthi, 2011). Based on data up to 2008, Chaves (2011) concluded that belief in God and frequency of prayer did not change in the General Social Survey (GSS) since the 1980s. Examining 18-to 24-year-olds in the GSS 1972-2006, Smith and Snell (2009 found only small changes in religious affiliation and service attendance, and no changes in frequency of prayer and belief in God. They concluded that emerging adults "have not since 1972 become dramatically less religious or more secular . . . if such a trend is indeed perceptible, it would seem to be weak and slight" (pp. 99-100). Other sociologists of religion have echoed these sentiments. Stark (1988, 2005) contended that the overall religiousness of the American public has remained relatively constant as a whole, although fluctuations in affiliation and expression have occurred. Similarly, Berger's (1999) work explored the overall constancy of American religious affiliation over time, with a particular focus on how religiousness moved back to the forefront of political and economic discourse in recent decades-sentiments also echoed in many other seminal works (Berger, 2011;Berger, Davie, & Fokas, 2008).
Thus, at least up to the mid-to late-2000s, research suggests that Americans' private religious practice and beliefs (e.g., those religious practices, disciplines, and beliefs that may be conducted alone or without explicit religious affiliation) and religious service attendance remained unchanged even as more did not affiliate with a particular religious tradition. Another possibility is that religious belief has been replaced by spirituality (Fuller, 2001;Saucier & Skrzypińska, 2006). In other words, the prevailing conclusion has been that Americans have remained just as religious and/or spiritual in a private or personal sense, but less religious in a public sense. This may be due to a more general disassociation from large groups-for example, Americans have become significantly less confident in virtually all large institutions from government to medicine (Twenge, Campbell, & Carter, 2014). Such an explanation would also be consistent with many popular conceptions of religion as a socially organizing institution (e.g., Ysseldyk, Matheson, & Anisman, 2010) that transmits cultural values, mores, and rules (Graham & Haidt, 2010). As societal norms have shifted away from institutional identification to individualism, one would expect commitment to religion, a ubiquitous social institution, to similarly decline. However, it is unclear whether such decreases in external commitment would also be associated with decreases in personal religious involvement or practice.
Despite popular conceptions that public religious involvement has decreased while private expressions of religion and spirituality have stayed about the same, stark distinctions between religion and spirituality may be more theoretical than practical. Although religion and spirituality are known to be distinct constructs (i.e., religion comprises social and ritualized aspects of personal belief, whereas spirituality includes the search for meaning or transcendence in daily life; Pargament, 1999), these two constructs often overlap, and highly religious individuals often identify as being highly spiritual as well (for a review, see Hill & Pargament, 2003). Moreover, although some individuals certainly do identify as spiritual but not religious (e.g., Saucier & Skrzypińska, 2006), a much larger proportion of individuals identify as both religious and spiritual (Pargament, 1999), and many people have difficulty substantively differentiating between the two on an individual level (Hill et al., 2000;Zinnbauer et al., 1997). Therefore, as religious commitment has decreased, one may also expect decreases in private religious practice and individual spirituality.
In this article, we seek to examine whether Americans' religious service attendance, religious practice, religious beliefs, religiosity, spirituality, confidence in religious institutions, and religious affiliation have changed since the 1970s, with a particular focus on the years since 2006 and on 18-to 29-year-olds. We take the additional step of calculating effect sizes and performing statistical significance testing to quantify the size of the changes. We draw from the nationally representative GSS of U.S. adults conducted 1972-2014. Because this survey draws from a multiage sample above 42 years, it can isolate the effects of age from those of time period and generation. 1 Thus, unlike some surveys conducted over a shorter period of time (e.g., 7 years: Pew Research Center, 2015), this data set can determine, for example, if the Millennial generation (born approximately 1980-1994) is less religious because they are young or because of generational or time period change. That is, are Millennials less religious than Generation X (born 1961-1979) and Boomers (born 1943Boomers (born -1960 were when they were 18-to 29-year-olds? This data may also provide an early look at iGen (born 1995-2012) and their religious attitudes.
Changes over time and generations in attitudes, values, and personality traits are rooted in cultural change (Stewart & Healy, 1989;Twenge, 2014), with cultures and individuals mutually influencing and constituting one another (Markus & Kitayama, 2010). One cultural change relevant for religious orientation is the rise in individualism, a cultural system placing more emphasis on the self and less on social rules (e.g., Bellah, Madsen, Sullivan, Swidler, & Tipton, 1985;Fukuyama, 1999;Myers, 2000;Twenge, 2014). Several studies have documented increases in focus on the self (Twenge, Campbell, & Gentile, 2013;Twenge & Foster, 2010) and declines in focus on institutions, empathy for others, and moral rules (Kesebir & Kesebir, 2012;Konrath, O'Brien, & Hsing, 2011;Twenge et al., 2014). There are several reasons we would expect religion to decline with greater individualism. First, religiosity implies some level of commitment to a larger group or organization. As Welzel (2013) suggests, the trend in Western societies has been toward more freedom and less commitment to groups. Second, belonging to a religious group may require assent with the group's beliefs, opinions, and practices. This can create tension when differences in opinion arise between an individual and an organization (e.g., Exline, Pargament, Grubbs, & Yali, 2014;Exline & Rose, 2013). Third, religiosity usually involves some rule-following and submission to authority (e.g., Graham & Haidt, 2010), another characteristic that goes against emancipation and individualism. Fourth, religion often focuses on concerns outside of the self, such as helping others and serving God (e.g., Pichon, Boccato, & Saroglou, 2007;Shariff & Norenzayan, 2007). Thus, the increasing individualism of American culture may have produced decreased religiosity among more recent time periods and generations.
Based on previous research and cultural changes, we expect a decline in religious affiliation. We also predict declines in religious service attendance; while religiously unaffiliated Americans may attend services for a time, they may become less likely to do so as they feel more disassociated from religion. Most crucially, we predict declines in more private expressions of religious belief and practice, such as prayer, religiosity, and belief in God, with the declines especially evident among young people. Belonging to a religion and more privately believing in its tenets are traditionally linked (e.g., Park et al., 2013;Smith, Denton, Faris, & Regnerus, 2002); as more Americans are unaffiliated with religion, a greater proportion may become not just unaffiliated but secular in their beliefs and practices. These declines may be especially evident in recent years and among 18-to 29-year-olds, given the generational and cultural trends toward emphasizing social rules less and individual freedom more (known as "Generation Me": Twenge, 2014;or "emancipative values": Welzel, 2013). Moving away from social institutions and community engagement would likely detract from one of the key facets of religion as a whole-that is, community involvement and social value transmission.
A secondary question is whether changes in religious orientation over time are caused by time period or generational (cohort) effects. If successive generations are less religious (forming their religious orientation while young and not changing), any decline would be due to generation. If people of all ages have become less religious during certain times, any decline would be due to time period. New hierarchical linear modeling techniques (called APC or age-periodcohort analyses) attempt to separate the effects of age, generation, and time period (Yang, 2008;Yang & Land, 2013). Some have argued that these techniques do not resolve the identification problem that has long plagued simultaneous analysis of age, period, and cohort effects (e.g., Bell & Jones, 2013; however, these criticisms appear to largely rest on untenable assumptions that are not consistent with basic APC models (Reither et al., 2015). In addition, APC techniques have become widely used. For example, Schwadel (2011) performed an APC analysis on some of the GSS religion variables up to 2006. However, at that time the data included only a handful of Millennials, a generation purported to be less religious; by 2014, however, Millennials were the entirety of 20-to 29-year-olds. In addition, further time period change may have occurred in the 8 years of data available since 2006. Thus, we perform APC analyses to examine whether shifts in Americans' religious orientation are due to generational or time period effects.
In addition, we examine possible moderators of change over time in religious orientation. Trends may differ among men and women, Blacks and Whites, education levels, and U.S. regions, as these groups differ in their levels of religiosity and cultural focus (Blaine & Crocker, 1995;Piff, Kraus, Cote, Cheng, & Keltner, 2010;Plaut, Markus, & Lachman, 2002;R. Taylor, Chatters, Jayakody, & Levin, 1996;Vandello & Cohen, 1999). We theorize that the decline in religious orientation will be larger among demographic groups and regions with higher social power and more individualism, including Whites, men, those with a college education, and living in the Northwest and West, and lower or nonexistent among groups with lower social power and less individualism, including Blacks, women, those without a college education, and the Midwest and South (e.g., Piff et al., 2010;Vandello & Cohen, 1999). Groups with relatively high social power might not see themselves as having a significant need for religion or God, so these groups might pioneer the movement toward less religiosity.
Thus, we have three goals in this article: (a) to perform a comprehensive examination of American adults' religious orientation from 1972 through 2014, with a particular emphasis on 2006-2014 and 18-to 29-year-olds, and including effect sizes; (b) to examine whether these changes are due to generation or time period; and (c) to examine whether the trends differ by gender, race, education, or U.S. region.

Sample
We drew from the GSS, 1972-2014, a nationally representative survey of U.S. residents over 18. Depending on the item, ns range between 12,862 and 58,893. As suggested by the GSS administrators, we weight the analyses by the weight variable WTSSALL to make the sample nationally representative of individuals rather than households and correct for other sampling biases. However, these weighted analyses differ only very slightly from unweighted analyses. Also as suggested by the administrators, we excluded the black oversamples collected in 1982 and 1987.

Items
We identified and analyzed all items on respondents' own religious orientation asked in at least six administrations of the GSS. They were as follows: 1. Religious preference: "What is your religious preference? Is it Protestant, Catholic, Jewish, some other religion, or no religion?" We analyzed the percentage of respondents who chose "no religion." Asked 1972-2014. 2. Strength of religious affiliation: "Would you call yourself a strong (Christian, Jew, etc.) or not a very strong (Christian, Jew, etc.)?" Response choices were "not very strong," "somewhat strong," and "strong." Asked 1974-2014. 3. Religious service attendance: "How often do you attend religious services?" Response choices were "never," "less than once a year," "about once a year," "about once or twice a year," "Several times a year," "about once a month," "2-3 times a month," "nearly every week," and "every week." Asked 1972-2014. 4. Belief in the afterlife: "Do you believe there is a life after death?" Response choices were "yes" and "no." Asked 1973-2014. 5. Believing the Bible is literal: "Which of these statements comes closest to describing your feelings about the Bible?" Response choices were "The Bible is an ancient book of fables, legends, history, and moral precepts recorded by men"; "The Bible is the inspired word of God but not everything in it should be taken literally, word for word"; and "The Bible is the actual word of God and is to be taken literally, word for word." Asked 1984-2014. 6. Frequency of praying: "About how often do you pray?" Response choices were "never," "less than once a week," "once a week," "several times a week," "once a day," and "several times a day." Asked 1983-2014. 7. Belief in God: "Please look at this card and tell me which of the statements comes closest to expressing what you believe about God." Response choices were "I don't believe in God"; "I don't know whether there is a God and I don't believe there is any way to find out"; "I don't believe in a personal God, but do believe in a Higher Power of some kind"; "I find myself believing in God some of the time, but not at others"; "While I have doubts, I feel that I do believe in God"; and "I know God really exists and I have no doubts about it." Asked 1988-2014. 8. Confidence in religious institutions: "I am going to name some institutions in this country. As far as the people running these institutions are concerned, would you say that you have a great deal of confidence, quite a lot of confidence, only some confidence, or very little in them?" One of the items is "organized religion." Response choices were "hardly any confidence at all," "only some confidence," or "a great deal of confidence." We excluded "don't know" and "refused" responses. Asked 1973-2014. 9. Identification as a religious person: "To what extent do you consider yourself a religious person?" Response choices of "not religious at all," "slightly religious," "moderately religious," and "very religious." Asked 1998 and 2006-2014. 10. Identification as a spiritual person: "To what extent do you consider yourself a spiritual person?" Response choices of "not spiritual at all," "slightly spiritual," "moderately spiritual," and "very spiritual." Asked 1998 and 2006-2014.
Of these, religious preference, strength of religious affiliation, religious service attendance, and confidence in religious institutions are public religious variables, and belief in an afterlife, believing the Bible is literal, frequency of praying, belief in God, identification as a religious person, and identification as a spiritual person are private religious variables.

Possible Moderators
We analyzed moderation by gender (men vs. women), race (White vs. Black, the only racial groups measured in all survey years), education level (high school graduate and below vs. attended some college and above), and U.S. region (Northeast, Midwest, South, and West).

Procedure
Data collected over time can be analyzed in many ways, including grouping by 20-year generation blocks, by decades, or by individual year. Given our focus on both overall change since the 1970s and change since 2006, we separated the data into 5-year intervals from 1972-2004 and reported data by individual year from 2006 to 2014. We report the effect sizes (d, or difference in terms of standard deviations) and p values for t tests comparing 1972-1974 with 2014 and 2006 and 2014. We also include two figures with all of the year-byyear data for some variables. We report both continuous variables (e.g., the 0-8 scale for religious service attendance) and dichotomous variables (e.g., the percentage who never attend religious services). We use the tables for means and report percentage changes in the text.
For the APC models, we estimated random coefficient models allowing intercepts to vary across time periods (years) and generations (cohorts). Thus, effectively, an intercept (mean religious orientation) score is calculated (using empirical Bayes) for each cohort and each survey year. In addition, a fixed intercept (grand mean) is estimated along with a fixed regression coefficient for age and age squared. This model has three variance components: One for variability in intercepts due to cohorts (τ u0 ), one for variability in intercepts due to period (τ v0 ), and a residual term containing unmodeled variance within cohorts and periods. Variance in the intercepts across time periods and cohorts indicates period and cohort differences, respectively (Yang & Land, 2013). Thus, the technique allows for a separation of the effects of generation/cohort, time period, and age. Weighting could not be used for the mixed-effects analyses because proper probability weighting for variance component estimation requires taking into account pairwise selection probabilities, which is not possible in current statistical software.

Trends in Religious Orientation
American adults in the 2010s were less religious than those in previous decades, based on religious service attendance and more private religious expressions such as belief in God, praying, identifying as a religious person, and believing the Bible is the word of God (see Table 1 and Figure 1).
These findings held when restricted to 18-to 29-year-olds (see Table 2 and Figure 2), demonstrating that Millennials  are less religious than previous generations were at the same age. 2 While religious affiliation and service attendance have been declining since the 1990s, the decrease in more private religious expressions began fairly recently, becoming pronounced only after 2006 (see Figures 1 and 2). Effect sizes ranged from moderate (around d = .50; Cohen, 1988) to small (around d = .20). The increase in never praying among 18-to 29-year-olds was d = .80, equaling the guideline for a large effect. As found in previous research, fewer Americans now affiliate with a religion. Although the majority of Americans are still religious, three times as many in 2014 (vs. the early 1970s) have no religious affiliation, and twice as many never attend religious services. Fewer have confidence in organized religion; the number who said they had "hardly any" confidence went from 14% in the early 1970s to 24% in 2014, a 71% increase, and those who said they had "a great deal" of confidence was cut in half (from 41% to 20%).
By 2014, the declines in religious orientation extended to more personal and private religious beliefs. Five times as many Americans in 2014 (vs. the late 1980s) never prayed (eight times more among those ages 18-29). Slightly more Americans in 2014 (vs. the 1980s) said they prayed "several times a day" (28%, up from 26%), but the 20% who prayed "less than once a week" in the 1980s became only 11% in 2014, apparently moving to "never" praying (3% in the 1980s vs. 15% in 2014).
Americans in 2014 were less likely to say they believed in God. In the late 1980s, only 13% of U.S. adults expressed serious doubts about the existence of God (choosing one of the less certain response choices such as "I don't believe in God"; "I don't know whether there is a God and I don't believe there is any way to find out"; or "I don't believe in a personal God, but do believe in a Higher Power of some kind"; these responses were combined into "Do not believe in God" in Tables 1 and 2). By 2014, however, 22% expressed doubts, a 69% increase. Among 18-to 29-year-olds, 30% had serious doubts by 2014, more than twice as many as in the late 1980s (12%).
Americans have also become less likely to believe that the Bible is the word of God. In 1984, 14% of Americans believed the Bible "is an ancient book of fables, legends, history, and moral precepts recorded by men" rather than the word of God; by 2014, 22% of Americans believed this, a 57% increase. Among 18-to 29-year-olds, 29% believed this by 2014, nearly twice as many as in the late 1980s (15%).
Has religiosity been replaced with spirituality? It does not appear so. Identifying as a spiritual person increased between 1998 and 2006, but then declined between 2006 and 2014 (see Table 1 and Figure 1). In all, 62% identified as moderately or strongly spiritual in 1998, compared with 70% in Figure 1. Percentage of all American adults with no religious affiliation, who never attend services, never pray, do not believe in God, are not religious at all, and are not spiritual at all.  2006 and 65% in 2014; thus, identification as a spiritual person increased 5% between 1998 and 2014, a small increase compared to the larger declines in religious belief and practice. In addition, the percentage of 18-to 29-year-olds identifying as moderately or strongly spiritual declined 6%, from 50% in 1998 to 47% in 2014. In 1998, 14% of 18-to 29-yearolds said they were not spiritual at all, rising to 19% by 2014, a 36% increase (see Table 2 and Figure 2). Thus, there is some suggestion that young people were less spiritual in 2014 versus 1998, though the decline was not statistically significant. In 2014, fewer 18-to 29-year-olds (Millennials) identified as spiritual (47%) than those 50 and above (72%). This suggests that identification as a spiritual person may continue to decline. One increase in religious belief did emerge: Slightly more Americans believe in life after death (see Tables 1 and 2). Thus, more Americans believe in life after death even as fewer belong to a religion, fewer attend religious services, and fewer pray. In the 1970s, only about 7% of Americans never attended religious services but nevertheless believed in life after death; by 2014, twice as many (15%) showed this disconnect between behavior and belief, and 21% among young people.

Mixed-Effects Analyses to Separate Time Period, Generation, and Age
First, we performed a principal components analysis to determine whether the religion variables could be combined into a composite variable for use in the mixed-effects APC model analyses; combining these variables into an index increases internal reliability over single items. (The religious person and spiritual person variables were not asked in enough years to be included, so we limited this analysis to the other eight variables.) We used the continuous form of six variables (strength of religious affiliation, religious service attendance, frequency of prayer, belief in God, belief in the Bible as literal, confidence in religious institutions), with religious affiliation (none vs. affiliated) and belief in an afterlife (yes vs. no) dichotomous. We included only respondents who completed at least four of the eight items. Horn's (1965) parallel analysis of n = 8,513 cases with no missing values indicated that only a one-component solution had an Eigenvalue better than chance levels. Moreover, all variables loaded highly onto a single principal component explaining 46% of the variance, with a model fit of .94 (on a 0-1 scale). Using the omega function available in the {psych} package in R (Revelle, 2015) indicated that 50% of the common variance in the item scores could be accounted for by a general factor of religious orientation. In addition, the omega coefficient, which is the best estimator of single factor saturation (see Zinbarg, Revelle, Yovel, & Li, 2005), was .70 suggesting that a single factor accounted for much of the variability in these items. The principal components analysis indicated a single principal component across the decades of data collection. Therefore, all variables were z scored, and a composite religious orientation variable was formed (n = 52,497, M = 0.01, SD = 0.69, α = .83).
Next, we performed mixed-effects analyses to separate the effects of time period, generation, and age on the composite variable. 3 The SD in intercepts for period (survey year) was .12 [.09, .16] and for cohorts was .03 [.00, .04], suggesting that almost none of the variability in religious orientation was due to cohorts. There was also a statistically Overall, there was a marked time period effect when generation and age were controlled (see Figure 3). Religious orientation declined d = −.38 from 1973 to 2014, and d = −.15 between 2006 and 2014. The generational effect was weaker, with religious orientation declining the most between those born in the 1930s and the Millennials born in the 1980s-1990s (d = −.06).
Although religious orientation formed a single factor, we also examined whether the pattern of change was different for public (affiliation, strength of affiliation, service attendance, confidence in religious institutions) and private (belief in the afterlife, belief that the Bible is literal, praying, belief in God) religious practice. Similar to the analyses with one combined variable, time period explained more of the change than birth cohort for both public and private religious practice. However, the pattern of change and its size differed (see Figure 4). The decline in public religious practice was larger (d = −.50 between 1972 and 2014, and d = −.42 between 1984 and 2014)

Moderators of the Decline in Religious Orientation
We next analyzed whether the time period and cohort decrease in religious orientation (controlled for each other and age) differed based on race, U.S. region, sex, and education level. The trends were moderated by race, with no change in religious orientation for Black Americans (d = .00) and a large decrease among White Americans (d = −.48). In the early 1970s, Whites and Blacks differed little in religious orientation (d = .15, 1973(d = .15, -1974, but by 2014, there was a marked racial difference, with Blacks higher (d = .67). Cohort effects were weak for both Whites and Blacks.
The effects also differed by U.S. region, with the decline in religious orientation largest in the West (d = −.42), Northeast (d = −.27), South (d = −.10), and Midwest (d = −.07). However, Midwesterners showed a pronounced cohort effect from those born in the 1880s to those born in the 1990s (d = −1.15), compared with the nonexistent cohort effects in the other three regions. In the early 1970s, Southern residents were only somewhat more religious than those in the Northeast (d = .23), but by the 2010s, Southerners were moderately higher in religious orientation compared to Northeasterners (d = .40). The West was the least religious region in both eras, with Westerners lower than Southerners in 1972 (d = −.47) but even more so in 2014 (d = −.78).
An intriguing pattern appeared when examining men and women separately: The time period difference was somewhat larger for women (d = −.28) than for men (d = −.12), but men showed a pronounced cohort decline in religious orientation (d = −.93), while women showed virtually no effect for cohort (d = −.02).
Similarly, the time period decline in religious orientation was somewhat larger among those who had not attended college (d = −.28) compared with those who attended at least some college (d = −.15). However, there was a moderate cohort decline in religious orientation among those who attended college (d = −.39) and virtually none for those who did not attend college (d = −.02). Overall, gender, race, education, and regional differences in religious commitment grew larger between the 1970s and the 2010s or between cohorts born in the late 19th century and those born in the late 20th century.

Discussion
By 2014, American adults were less likely to pray, believe in God, identify as religious, attend religious services, or believe the Bible was the word of God than they were in previous decades. Thus, the decline in religious affiliation found in previous research has now extended to religious service attendance and, by 2008 and afterward, to personal religious belief and practice. The only exceptions were an increase in belief in the afterlife and a small increase in identifying as spiritual between 1998 and 2006 limited to those above 30. The declines in religious orientation were particularly striking between the early 2000s and 2014 and among those 18 to 29 years old. Nearly a third of Millennials are not just religiously unaffiliated, but secular in other ways (doubting the existence of God, believing the Bible is a book of fables, not attending religious services, describing oneself as "not religious at all," never praying), and one out of five also say they are "not spiritual at all." Although religious orientation is often conceptualized as a multidimensional concept (e.g., Cornwall, Albrecht, Cunningham, & Pitcher, 1986;Idler et al., 2003), the present data indicated that declines in religious affiliation extended across various measures of religious participation and commitment. The decline in religious affiliation and participation has now extended to private practices and beliefs, though the decline in private religious practice and belief is smaller and began later than the decline in public religious practice.
Mixed-effects analyses demonstrated that these trends were primarily due to time period. Millennials were less religious than their Boomer and Generation X predecessors were at the same age, demonstrating that their lower religious commitment is not solely due to their developmental stage of young adulthood. However, this appears to be due to a time period effect in which all generations are growing less religious over time. This suggests support for the idea that growing individualism has been accompanied by less religion on a larger cultural basis, with a larger linear cohort decline in some groups (men, Midwesterners, the college educated). These findings contradict popular culture notions of generations cycling back and forth with, for example, a less religious generation being followed by a more religious one. For example, generational theorists Howe and Strauss (2000), who adhere to the theory that generations come in cycles, proposed that Millennials would be more religious than GenX'ers. However, these data strongly suggest that the opposite is true.
Men and women, Blacks and Whites, the college educated and not college educated, and the South versus the Northeast are becoming more polarized in their religious orientation: While differences in religious commitment between these groups were small during the 1970s, they have grown larger in recent years and with recent cohorts. The decline in religious commitment was most pronounced among men, Whites, and those in the Midwest, Northeast, and West, and was nearly absent among Black Americans and small in the South. It appears that groups with relatively high social power are less likely to see themselves as having a significant need for religion or God in recent years.
In comparison with those from earlier years and generations, American adults in recent years and generations were slightly more likely to believe in an afterlife. Combined with the decline in religious participation and belief, this might seem paradoxical. One plausible, though speculative, explanation is that this is another example of the rise in entitlement-expecting special privileges without effort (Campbell, Bonacci, Shelton, Exline, & Bushman, 2004;Twenge & Foster, 2010). Entitlement appears in religious and spiritual domains when people see themselves as deserving spiritual rewards or blessings due to their special status. Entitlement centered on afterlife beliefs could be seen as a modern rendition of Pascal's wager, in which the individual observes that believing in God and a positive afterlife has few downsides, but not believing has the major possible downside of condemnation to eternal suffering (Hájek, 2003). However, the current data make it difficult to determine the cause of rising belief in the afterlife.

Limitations and Future Directions
Using the GSS data set has several major advantages, including the ability to examine trends among carefully sampled U.S. adults over long periods of time. Nonetheless, this form of research also has its limitations. Responses are limited to self-report, and measures must be brief. As such, the GSS does not provide the opportunity for nuanced or in-depth measurement of specific ideas of interest over time.
Principal component and omega analyses demonstrated that a single factor captured the eight religious orientation variables. Although religiosity is usually conceptualized as multidimensional (Cornwall et al., 1986;Idler et al., 2003), in this data set, the majority of variation in religious orientation was determined by a single factor. We tried to strike a balance between internal reliability and diversity among individual items by presenting analyses of single items in the tables and focusing the APC analyses on the composite measure and on the public and private practice measures.
Our focus here was on individuals in the United States, so cross-cultural studies should examine temporal trends in religious orientation in other countries. Religious groups may also differ in how they manage the discrepancy between religious participation and afterlife beliefs, based on teachings about the afterlife and whether (and how) the afterlife is connected with choices or behaviors during this life.

Conclusion
The 2010s are a time of tremendous change in the religious landscape of the United States. Although the majority of Americans are still religious, the declines in public religious affiliation observed in previous research have, by 2014, extended to private religious belief and action (such as prayer, belief in God, and identifying as religious). This decline was not replaced by a substantial increase in those identifying as spiritual. The slight increases in afterlife belief represent a potentially important exception to this pattern. Overall, the data suggest a pervasive decline in religious participation and belief among Americans, with a burgeoning minority becoming decidedly nonreligious.

Declaration of Conflicting Interests
The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding
The author(s) received no financial support for the research and/or authorship of this article.

Notes
1. Birth cohort refers to everyone born in a given year, and generation to those born within a specified period. Both refer to the effects of being born during a certain era and thus are thus somewhat interchangeable; we will use the term generation most of the time but will use birth cohort when we are specifically referring to birth year. Generational labels (such as Boomers and Millennials) use arbitrary birth year cutoffs; we use these labels only for ease of presentation. 2. In the 2014 survey year, the 18-and 19-year-olds were born after 1995 and thus are iGen instead of Millennials. The n of 18-to 19-year-olds was too small to justify a separate analysis (e.g., n = 51 in 2014). As a proxy, we examined 18-to 22-yearolds (n = 153 in 2014; total n 1972-2014 = 4,927), which in 2014 includes those born 1992-1996 (and thus, those at the cusp between Millennials and iGen). In most cases, the decline in religious orientation was even more dramatic among 18-to 22-year-olds than among 18-to 29-year-olds. For example, the percentage of 18-to 22-year-olds who reported no religious affiliation rose from 11% in 1972-1974 to 36% in 2014; the percentage who reported they never prayed rose from 4% in 1980-1984 to 28% in 2014; the percentage who said they were "not spiritual at all" rose from 13% in 2006 to 25% in 2014. Belief in God declined d = -.54 , being a spiritual person d = -.21 (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), and attendance at religious services declined d = -.48 . This suggests that iGen will continue the decrease in religious orientation rather than reversing it, even in spirituality. 3. Some controversy has surrounded the issue of which intervals to use in APC models (Bell & Jones, 2013. We analyzed the data in 2-year, 5-year, and 10-year intervals, and found that they all produced very similar results.