Having supportive friends raised the share of couples intending to have another child from around 30 percent to about 45 percent. Put simply: ambient culture sets the aspiration, but real-world friends lead to actual births. A society can be awash in pro-family influencers and still be barren if nobody is willing to babysit. Friendship, though, is collapsing. The number of close friends Americans report has been falling for decades. Time spent with friends has dropped sharply, particularly for the young. 

In 1775, a Harvard professor named Edward Wigglesworth sat down and did some math. The American colonies were doubling in population every 20 years, primarily due to a high birth rate. Projecting forward, he calculated that by the year 2000, America would have a population of 1.28 billion people. He wrote the number in capital letters, as he was so overwhelmed by the thought.

When the year 2000 arrived, we came in about a billion short.

A new report from the Institute for Family Studies, “The Demographic Dead End,” opens with Wigglesworth’s forecast and then explains, in careful and sometimes alarming detail, why it failed and what comes next. The authors, demographer Lyman Stone and researcher Peter Foreshaw Brookes, have built what they call the most reliable published reconstruction of historic American fertility: birth rates for every state back to 1917, and for Massachusetts back to 1660. The report was released to mark the country’s 250th birthday.

The headline finding is simple. The American birthrate has fallen below 1.6 children per woman. Replacement fertility requires about 2.1. The United States is now in its third extended period of below-replacement fertility, after the Great Depression years and a stretch from 1972 to 1989. The current period, though, has lasted longer and fallen lower than either of the previous two. If the trend continues, Stone and Brookes project that the American population will peak around 351 million in the 2050s and then decline.

Why? Here the authors have uncovered something genuinely novel: evidence that the fertility collapse is not only economic, but social. Americans are not having fewer children because they want fewer children. They are having fewer children, in part, because friendship has thinned and social support for family life has weakened.

Surveys show that Americans want more children than they are likely to have. The IFS report puts desired family size at about 2.4 children on average; a 2025 Gallup survey found an even higher ideal family size of 2.7 children. Americans are actually on track for fewer than 1.6. The gap between desired and actual family size is the widest it has been since the early 1970s.

So what is blocking people? The standard answers are money and housing, and the report takes those seriously. But its centerpiece is a new survey of 4,784 Americans between 18 and 50, and the results point somewhere else: at peer culture.

The researchers asked respondents how many kids their three closest friends had, and how those friends would react if the respondent had another baby. Would they offer to help? Cook meals after the birth? Or would they worry about their career stalling or stop inviting them out?

Read More