How do fertility rates compare among different religious groups in the US?
Executive summary
Religious Americans generally have higher fertility than the religiously unaffiliated: studies show weekly-attending or highly religious women average near or above replacement-level fertility while nonreligious Americans average well below it (NSFG/DIFS analysis; Institute for Family Studies) [1]. Pew’s large surveys likewise find Christians report higher completed fertility (about 2.2 children) than the unaffiliated and non-Christian groups (about 1.8 each) [2] [3].
1. The widening religiosity gap: who’s having more children
Multiple sources document a persistent and growing gap in fertility by religiosity: women who attend religious services weekly or identify as devout have fertility that has declined much less than that of nonreligious Americans, with some estimates putting weekly-attenders at roughly two children per woman and the unaffiliated considerably lower (IFS analysis of NSFG and DIFS data; Newsweek reporting summarizing that analysis) [1] [4].
2. Affiliation matters, but so does intensity
Beyond the broad “Christian vs. unaffiliated” headline, completed-fertility figures differ by subgroup: Pew’s Religious Landscape Study finds Christians on average report about 2.2 children versus about 1.8 for religiously unaffiliated and other non-Christian groups, while earlier Pew demographic profiles showed “nones,” atheists and agnostics averaging roughly 1.3–1.7 children depending on category [2] [3]. Historical academic work also highlights higher fertility among frequent-attending Protestants and especially high fertility in Mormon communities, with Jews and some other groups closer to or below replacement in older data [5] [6].
3. Mechanisms researchers identify: behavior, timing and contraception
Scholars point to several mechanisms linking religion and births: religious attendance and practice influence marriage timing, childbearing intentions and contraception use—religious women are on average less likely to use contraception or use less effective methods, and attendance correlates with practical family decisions like enrolling children in religious activities—factors that raise realized fertility relative to secular peers (PMC analysis of NSFG; p1_s3). Age and marriage patterns also mediate differences: some groups report more children over a lifetime in part because their members are older or marry earlier (Pew) [2].
4. What projections say about future composition
Demographic projections incorporate these fertility differentials: Pew’s projection work assumes fertility differentials persist and shows Christians remain the largest group but grow more slowly than higher-fertility non-Christian groups and immigrants; Muslims in North America were estimated at a higher TFR (~2.7 in 2010–15) while Jews and the unaffiliated were noted as below replacement in some panels [7] [8]. Analysts caution that switching, migration and transmission to children also shape long-term religious demography and that assumptions (e.g., constant fertility differentials) matter for forecasts [8].
5. Variation across studies and important caveats
Estimates vary by data source, measure (children ever born vs. total fertility rate vs. completed fertility), time period and whether religiosity is measured by affiliation, attendance or self-rated importance; different surveys and time windows produce different point estimates, and some sources emphasize rising nonreligion even while its fertility is low [1] [3] [8]. Academic work warns about reverse causation—having children can increase religious engagement—and about unwanted fertility inflating observed differences, so causality is complex [9].
6. How reporting and advocacy shape the conversation
Media and advocacy outlets frame the facts through agendas: conservative or religious commentators emphasize secularization as a driver of low births and cultural decline, while demographers focus on multifactorial causes—economics, education, contraception and switching—and treat religion as one influential variable among many (Newsweek summary; Survey Center newsletter) [4] [10]. Readers should note when authors use attendance-based measures (practical practice) versus identity-based measures (self-label) because those choices shift the headline.
7. Bottom line
Across reputable surveys and demographic analyses, religiosity correlates with higher fertility in the U.S.: weekly-attending or devout religious Americans tend to have larger families, Christians as a broad group report higher completed fertility than the unaffiliated, and smaller or non-Christian groups show more mixed patterns—yet differences are mediated by age, marriage, contraception, switching and immigration, and estimates depend on data and definitions [1] [2] [9] [7].