As Facebook's monthly active users have grown, the US fertility rate has declined, a negative correlation of -0.982 that will be cited by exactly the kind of person who posts "kids these days" on Facebook without irony. The timeline fills, the cribs empty, and the chart suggests that social media is replacing reproduction, which is the kind of conclusion that your aunt would share without reading the fine print.
Facebook MAUs grew from about 1.7 billion to over 3 billion between 2015 and 2022. The US fertility rate declined from about 62 to 56 births per 1,000 women of childbearing age. Both are smooth curves: Facebook up because global adoption continued, fertility down because economic pressures, delayed marriage, and expanded contraceptive access reduced birth rates. The correlation is real in the sense that both trends are driven by the same modernizing forces—but Facebook did not cause the fertility decline any more than television did in previous decades.
Eight years of Facebook and fertility is a correlation that sounds like a thesis and is actually just two trends shaped by the same modernization. The feed scrolls, the birth rate falls, and the shared variable is a world where screens provide stimulation and children require sacrifice. The algorithm engages. The ovary declines. The causation is elsewhere.
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Want to learn more about why correlations like “US fertility rate” vs “Facebook monthly active users” don't prove causation? Read our guide to statistical thinking.
