In theory, the Constitution requires every man, woman and child to be counted every 10 years. In practice, the 2010 Census saw about a million children nationwide slip through the cracks.

Using an analysis of birth rates, the U.S. Census Bureau estimates that the last census missed 4.6% of children under five. In Colorado, the bureau estimates that 16,400 in that age group were missed. The estimated percentage of undercounted children has steadily increased since 1980, when it was 1.4%.

“I always have to have a graphic to think about numbers, and for me that would be the city of San Antonio,” Pauline Núñez, partnership coordinator for the U.S. Census Bureau-Denver Region, said Tuesday. “It’s about one million and change, and that’s how many children were missed in 2010.”

That many children being undercounted can lead to under-representation — seats in the U.S. House of Representatives are given proportionally to states based on population and state legislative districts are redrawn based on population. An undercount can also financially harm states and communities, who miss out on federal funds distributed by population to a wide variety of programs, including education, food assistance, healthcare, housing, loans and transportation. The most recent study by the Census Bureau found that $675 billion was distributed by federal agencies or programs to the states in 2015, and more than $13 billion in federal dollars went to Colorado in 2016.

Núñez spoke at the Early Childhood Summit on Sept. 24 and 25 in Denver aimed at addressing early childhood undercounts, bringing educators and community representatives from Western states, including Texas, Arizona, New Mexico and Oklahoma, as well as representatives from the Pueblo and Comanche Nations.

Among the characteristics of households where there might be an undercount, according to the Census Bureau:

Lower income

Divorced parents, which could lead to children moving often

Young or single parents

Newborn children

Non-English or limited-English speaking households, or in households with recent immigrants.

A 2014 report from the Census Bureau said that one reason for the 2010 undercount was the result of surveyors’ errors — interviewers not following up with a family, mistaking an address, or not understanding whom to include as a member of the household. Another cause: people either not understanding or mistakenly answering the questions. There is also a reluctance to participate due to fear or mistrust of government. This latter reason is a particular concern among organizations trying to encourage undocumented residents of the U.S. to participate in the census.

The bureau does not have concrete data for how many children in Colorado’s immigrant population were undercounted in 2010, but Cathy Lacy, director of the U.S. Census Bureau’s Denver Regional Office, said in an interview with The Colorado Independent that an undercount among immigrants could be the result of not understanding what the census is, “or it could be they’re coming from a country where a census is something negative.”

The Trump administration tried to add a citizenship question to the 2020 census, but stopped its efforts in July. When asked if lingering fear around that effort might dampen participation, Lacy didn’t give an answer, and instead stressed local recruiting to increase cooperation among immigrants.

“We’ve done a greater job of working with our complete count committees, local and state government to make sure this is a positive thing,” Lacy said.

Rosemary Rodriguez, executive director of the census-engagement organization Together We Count, wrote in an email to The Colorado Independent that not only the citizenship question causes fear, but so does the language used in the national conversation about immigrants.

“They are paying attention to the national news and discourse and for some, it is creating an atmosphere of feeling targeted, isolated and excluded,” she wrote.

For example, Rodriguz said the responses to the citizenship question on the American Community Survey, which is sent to a small percentage of US residents annually, has declined in recent years.

Undercounting children has been a problem for decades, according to the Census Bureau. Lacy said the bureau is purposely focusing on educating its surveyors about the possible causes of undercounts in 2010, as a way to improve the count in 2020.

The bureau has been working with early childhood educators, like the ones at the Early Childhood Summit, Lacy said, to bring the education about the census into schools and get the word out about undercounts.

Emphasis will be placed on hiring members of the communities the census is surveying, Lacy said, adding that the bureau is recruiting workers who— speak the language of the households being surveyed or who volunteer with community organizations.