A Brief History of the Census—and How Covid-19 Could Change It

THE UNITED STATES is currently undertaking its population census, the once-a-decade effort to count every single person living here. More than 150 other countries will join in this world census round—the 10-year period centered on 2020, and around 90 percent of the world’s population has already been or will be counted.

But while impressive on a human scale, a modern census is technologically unspectacular. The American questionnaire asks just seven questions of each person, with a few more for each household as a whole. Counting generously, the government is collecting 130 bytes of data per person and perhaps another 13 bytes per household—amounting to around 45 GB for the whole US population. If it weren’t for the strict confidentiality, you could, once it’s complete, carry around the entire contents of the US census on a base model iPhone 11. The challenges of this year’s census are enormous, but they are social, political, logistical—and now public-health related—rather than strictly technological or scientific.

That wasn’t always the case: For centuries, counting its people was amongst the most technologically complex procedures a state could undertake. It’s not possible to point to a first census: Such a simple idea likely arose independently many times and in many places. Although writing is now integral to how we record, analyze, and report data, census-taking certainly predated it. Herodotus relates a story of the Scythians, nomadic warriors who lived in Central Asia in the first millennium BCE. “Because their king, who went by the name of Ariantas, wished to know how many Scythians there were, he gave orders that each one of them was to bring an arrowhead ... A huge number of arrowheads were duly brought, and the king”—presumably having first counted them—“decided to fashion a monument out of them that he could bequeath to posterity.” Such a method would be a bit unwieldy today, but it probably worked fine for the Scythians.