Photo: Paul Kuroda / Special To The Chronicle

The size of your child’s kindergarten class. Homeland security funds for your community. Natural disaster preparation. Highway and mass transit resources. Health care and emergency room services.

Vital services such as these would be jeopardized and our voice in government diminished if the U.S. Census Bureau’s 2020 count resulted in an undercount. Beyond its constitutional role in redistricting, a proper count conducted by the U.S. Census Bureau shapes our everyday lives. If the bureau is ill-prepared for the job or a count is faulty, every state, every neighborhood, faces the risk of losing its fair share of federal funding for its people and its taxpayers.

Every 10 years, the bureau must count each person in our country — whether citizen or noncitizen — “once, only once, and in the right place.”

The Trump administration is threatening to derail the integrity of the census by seeking to add a question relating to citizenship to the 2020 census questionnaire. Innocuous at first blush, its effect would be truly insidious. It would discourage noncitizens and their citizen family members from responding to the census, resulting in a less accurate population count.

Including a citizenship question on the 2020 census is not just a bad idea — it is illegal.

The Constitution requires the government to conduct an “actual enumeration” of the total population, regardless of citizenship status. And since 1790, the census has counted citizens and noncitizens alike.

The census has a specific constitutional purpose: to provide an accurate count of all residents, which then allows for proper allotment of congressional representatives to the states. The Census Bureau has a long history of working to ensure the most accurate count of the U.S. population in a nonpartisan manner, based on scientific principles.

Since the last census in 2010, the public servants at the Census Bureau have been planning and fine-tuning the 2020 census. This work includes painstaking determinations of which questions to ask on the census and how to ask them.

In December, the U.S. Department of Justice formally asked the bureau to include a question on citizenship in the 2020 census. By March 31, Commerce Secretary Wilbur Ross must decide whether to add this question.

This request is an extraordinary attempt by the Trump administration to hijack the 2020 census for political purposes. Since the first day of his presidential campaign and through his first year in office, President Trump has targeted immigrants: vilifying them and attempting to exclude them from the country. Think travel bans, repeal of Deferred Action for Childhood Arrivals, ramped up Immigration and Customs Enforcement raids that tear parents away from their children. Immigrants and their loved ones understandably are, and will be, concerned about how data collected in the 2020 Census will be used.

California, with its large immigrant communities, would be disproportionately harmed by depressed participation in the 2020 census. An undercount would threaten at least one of California’s seats in the House of Representatives (and, by extension, an elector in the electoral college.) It would deprive California and its cities and counties of their fair share of billions of dollars in federal funds.

These concerns are real and they are bipartisan. The past four census directors, who served under both Republican and Democratic presidents, have all publicly voiced opposition to a citizenship question based on the certain consequence of an undercount. These concerns affect red states and blue states alike.

The politicization of the 2020 census must stop now. By the end of the week, the bureau will announce its final list of census questions. Secretary Ross should uphold the government’s constitutional duty to count all people in every part of the country — and reject the Justice Department’s dangerous call to add a citizenship question to the 2020 census.