The enduring mystery of fertility decline has a new culprit: Smartphone

Experts have long wondered if phones played a role in the birthrate decline — which began in 2007, the same year that Apple introduced the iPhone — but until now there had not been hard evidence to prove it.

- SABRINA TAVERNISE

Two new papers, one published Monday and the other in May, are the first academic endeavours that test whether the smartphone was a cause.

They are the most recent efforts to explain the sweeping fertility rate decline in the United States and other countries over the past 20 years. Researchers have already looked at contraception use, abortion rates, rising levels of female education and even the popular television show “16 and Pregnant.”

Proving phones caused the decline is a tricky endeavour. There were a number of major events in those years, including the Great Recession, and isolating smartphone use is difficult.

The gold standard for scientific evidence is known as random assignment. It compares outcomes for people randomly chosen to receive a treatment (like getting a smartphone) with people who are not.

But that is not possible when it comes to ferreting out reasons for declining fertility.

So researchers sought out data about smartphones that introduced randomness.