The collapse of teen fertility in the digital era – Marginal REVOLUTION

Once enough teens are on the phone, being on the phone is where the peer network is; in-person time falls sharply, and with it the unstructured contact in which most unintended teen conceptions occur. A coordination model formalizes this tipping: as the smartphone price falls, the in-person equilibrium ceases to exist and the economy moves to a phone-mediated one. Within the United States, terrainruggedness variation in broadband and 4G coverage identifies a causal effect on teen fertility, and time-use diaries show in-person socializing among teens roughly halving while digital leisure roughly tripled. A parallel design for England and Wales recovers the same acceleration and the same effect of mobile coverage on teen conceptions, ruling out country-specific contraceptive-access and welfare-reform stories. The model predicts that the shift towards the phone-mediated equilibrium affects multiple aspects of teen behavior. The same instrument that produces a collapse in teen fertility produces a surge in teen suicides.
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