Does smartphone adoption reduce teenage fertility rates?
Core argument: Smartphone diffusion reduces face-to-face dating and sexual activity among adolescents, leading to 6.6% fewer births among women aged 20–24 in.
The general fertility rate (GFR) — annual live births per 1,000 women aged 15–44 — remained roughly constant at 65 to 70 from 1980 through 2007, then began a sharp decline that has continued for nearly two decades. The iPhone, which was launched in June 2007, diffused rapidly across every demographic group and is consequential for how young adults spend their time. The cohorts whose adolescence overlapped with smartphone diffusion spend sharply less time on face-to-face socialising, dating, paid work, drinking, and driving, and report fewer sexual partners and rising sexual inactivity in young adulthood. Figure 4 reports the results of an SDID (synthetic differences in differences) event study by five-year age band. At ages 15–19, the average ATT coverage effect on fertility is −8.0%, and at ages 20–24, the ATT is −6.6% (p < 0.01). It is much smaller, but still statistically significant for the older cohorts. Figure 6 uses the results of these analyses to produce adjusted predictions of the log fertility rate in an alternate world in which the iPhone was not introduced in 2007. Figure 9 shows in-person social interaction and psychological well-being, for the isolation channel; Figure 10 shows pornography access. These are descriptive trends in nationally representative survey data, consistent with the channels we propose but not a test of any of them.

