It is a wonderful fact that Japan has roughly one vending machine for every 23 people, and a less wonderful fact that American fertility has been drifting downward for decades. That these two facts move in lockstep is the sort of thing that makes demographers reach for a drink they just bought from a vending machine.
Japanese vending machine counts have been gently declining for years — young Japanese drink less, rent is rising, and convenience stores have eaten into the business — while the US fertility rate has been sliding through two long secular trends that each took a sharper drop in 2020 as covid scrambled plans. Neither causes the other; both are long declines that happened to steepen in the same pandemic year. The shared variable is demographic pessimism.
So the correlation is a quiet memo from the 21st century: fewer coins, fewer cribs. Both societies changed the math on what they were willing to invest in. The machines, at least, still take cash.
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Want to learn more about why correlations like “US fertility rate” vs “Japanese vending machines” don't prove causation? Read our guide to statistical thinking.
