Pedestrian traffic fatalities

It turns out that as Japan's population has gently declined from 127 million people to 125 million between 2014 and 2022, pedestrian traffic fatalities have marched steadily downward in perfect lockstep, as though the country's roads had simply decided to become safer the moment fewer people existed to walk on them. One might reasonably wonder whether Japan's aging and shrinking population has discovered the ultimate traffic safety measure: staying home. The correlation is remarkable, the causation invisible.

What's actually happening here is almost certainly not that fewer Japanese people somehow kill fewer Japanese people through a mysterious demographic osmosis. Instead, Japan experienced two genuine trends that merely waltzed past each other in opposite directions: as the population aged and declined, younger drivers—statistically more reckless, more likely to speed through residential areas, more inclined to text while navigating—became proportionally rarer. Meanwhile, over these nine years, Japan's already exceptional infrastructure improved further, autonomous safety systems became standard in new vehicles, and elderly drivers increasingly retired from roads. The physical reality is staggering: Japan went from roughly 4,400 pedestrian deaths annually to 2,800, a drop of about 1,600 lives, while its population shrank by merely 1.6 percent.

This is what happens when you feed a computer nine years of data and ask it to find patterns without judgment—it obliges, indifferent to whether those patterns mean anything at all. Japan's population decline and road safety improvements are genuinely unrelated phenomena that happened to move in the same direction, a reminder that the universe contains far more coincidences than conspiracies. Correlation remains, as always, a magnificent liar.