From 2007 through 2024, the U.S. birth rate steadily declined after nearly three decades of relative stability.

While some have speculated that the decline stems from socioeconomic factors — such as the cost of health care, child care or housing — researchers suggest there may be another culprit: the iPhone.

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Since 2007, the U.S. fertility rate — broadly defined as the number of children women ages 18 to 45 have in a given year — has dropped 22%.

A paper released this week by the National Bureau of Economic Research found that the advent of the iPhone and other smartphones reduced relationship formation and partnered intimacy. The study noted that smartphones were not the sole cause of declining fertility, but they could account for nearly half of the drop.

Researchers focused on the period from 2008 through 2011, when many Americans began shifting from flip phones to smartphones.

The paper argues that more than simply enabling broader smartphone use, these devices made it easier for Americans to access pornographic material, reducing the need for a sexual partner. Researchers also cited increased stress and reduced social contact outside of family as other factors emerging from the smartphone era.

The authors said financial incentives for having children — such as those proposed by the Trump administration — would have only modest effects on boosting birth rates, and that such incentives would come at a “steep cost.”

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“We do not claim that the iPhone is the sole cause of the post-2007 decline, nor that no policy lever can move the trajectory,” the paper says. “But over the 2008–2011 window that our design identifies, our estimates imply that the introduction of the modern smartphone played a sizable role in the decline in U.S. births.

“The mechanism evidence suggests this operates through the formation of relationships and the time and inclination for partnered intimacy, not the cost of raising children. If so, the policy instruments to which governments have committed the largest sums — cash transfers, tax credits, subsidized childcare, extended parental leave — do not, on their own, address the behavioral shift our estimates suggest is at work.”