The census, conducted once every 10 years, is the largest mobilization of civilians in the United States, requiring years of research and preparation.
While there are myriad ways to estimate the U.S. population, only the census is intended to count every last person in the country. While it has never succeeded in counting everyone, it is the closest the country gets to “the whole number of free persons” demanded by the U.S. Constitution.
And it is an undertaking. The first census counted 3.9 million “people” — enslaved people were counted as only three-fifths of a person — but by 2010, it took a full million people just to conduct the census, which enumerated the country’s more than 300 million inhabitants.
Between 1790 and 1870, the census was conducted by U.S. marshals. From 1880 on, the once-a-decade count has been conducted by specially trained enumerators, now overseen by the U.S. Census Bureau.
By law, the country is required to conduct the census, and its residents are also legally required to respond, though no one has been prosecuted for failing to respond to the decennial census in more than 50 years, according to the Census Bureau.
In 2020, U.S. residents began receiving notices and forms in the mail in the early spring. In a bid to lower the costs of the greatest non-military project the country conducts, as well as to increase response rates, the 2020 Census was the first in history to allow responses to be submitted online, in addition to tradition mail or phone responses.
Those who did not immediately respond were sent up to five follow-up notices by mail; if a resident continues not to respond, the enumerators are meant to come into play. For up to six days, enumerators are supposed to knock on a resident’s door and attempt to gather census information from someone in the household. After three days of attempting to make contact, an enumerator may even ask neighbors to fill in the information for the nonresponding household by proxy.
The process has never been perfect, and the Census Bureau conducts audits after each decennial census to determine the extent to which certain communities are over or undercounted. But the 2020 Census, the 24th in the nation’s history, is here to stay.