An American flag flies in front of the Atlanta VA Medical Center in Atlanta. (David Goldman/AP).

The NAACP is suing the Trump administration over what it sees as inadequate preparation for the 2020 Census, a problem the civil-rights group claims is likely to lead to severe undercounting of minorities.

On Thursday, the NAACP filed a lawsuit in federal court alleging the Commerce Department, which oversees the Census Bureau, is “unlawfully withholding” information about its plans for the 2020 Census, especially regarding how it will get the word out to minority and low-income communities.

“The Census Bureau routinely undercounts communities of color, young children, home renters, low-income persons, and rural residents,” said Bradford Berry, general counsel for the NAACP. “All signs indicate that the 2020 Census will be a particularly egregious failure on this front.”

Commerce Secretary Wilbur Ross said the lawsuit is “largely without merit” in a statement to The Washington Post.

“The Census Bureau is committed to assuring a full, fair and accurate count, and I pledge to oversee the Bureau’s efforts to discharge that commitment,” Ross said.

The census plays a critical role in America’s democracy. The U.S. Constitution requires the federal government to conduct a census once every 10 years to figure out how many people live in the country and exactly where they reside. The results of the census determine how many congressional seats each state gets. Many states also use the census results to draw congressional districts.

“If we aren’t counted, then we don’t count,” said Scot Esdaile, president of the NAACP’s Connecticut State Conference, which is joining the lawsuit.

Census data also helps determine where $600 billion in federal funds go each year for everything from highway funding to law enforcement to Medicaid, the program for low-income health care.

In June, the NAACP filed a Freedom of Information Act (FOIA) request to obtain documents on the Census 2020 outreach, testing and hiring plans to ensure “hard-to-count” populations fill in their forms. The Commerce Department responded to the FOIA in the past week with about a hundred pages of documents, mostly showing how many people the census has hired in recent years. The NAACP’s lawyer called it a “wholly inadequate” response that shows the Trump administration doesn't want to be transparent about the census.

Some of the funding for the census is supposed to go toward media and outreach campaigns to educate people on how to fill out census forms and why it’s critical to do it. In 2020, the census is planning to ask Americans to fill out the form online for the first time. The NAACP is worried that many people of color don’t have Internet access and that the census has not tested the online platform sufficiently.

The NAACP isn’t the only group raising serious concerns about how unprepared the Census Bureau is for 2020. Experts across the political spectrum and many former census directors warn that Congress and the Trump administration are underfunding the census.

Congress wants the 2020 Census to cost the same amount of money — about $12.5 billion — as the 2010 Census. Experts point out there are many reasons funding should go up. The U.S. population is bigger now, and a dollar today isn't worth as much as a decade ago. According to the government's own inflation calculator, it costs more than $14 billion today to get what you did with $12.5 billion in 2010.

Congress is currently debating how much money to give the Census Bureau in 2018, a critical year when the census typically tests the tools it plans to use for the big decennial census.

Kenneth Prewitt, who directed the census from 1998 to 2000 and is currently a professor at Columbia University, thinks the census needs at least $2 billion next year to be able to do a good test run of the online tools. The Trump administration asked for less than $1.5 billion.

“Any ramp up year with less than $2 billion in funding will handicap the census,” Prewitt said.

On top of the funding concerns, the Census Bureau doesn’t currently have a director. John Thompson, the prior director, resigned abruptly in May. He has yet to be replaced. Commerce Secretary Wilbur Ross told The Washington Post on Sept. 8 that he’s “actively searching” for a new director. Nearly a month later, no announcement has been made. The acting director is still in place.

“The lawsuit is a shot across the bow to the Trump administration and Congress that Americans will not settle for a census that continues to miss vulnerable populations,” said Terri Ann Lowenthal, who worked for many years as a leading census expert in the House of Representatives and then directed the Census Project, a nonpartisan group supporting the census.

Conservative and liberal think tanks don’t agree on much, but the right-leaning American Enterprise Institute and the left-leaning Center on Budget and Policy Priorities sent a joint letter to Congress in late September warning the 2020 Census isn’t going to be accurate unless Congress increases funding substantially.

“Policymakers and businesses can’t make good decisions without good data,” says Arloc Sherman, a longtime fellow at the Center on Budget and Policy Priorities.

To save money, the census is hoping many people will fill out the firms in 2020 online, but it has yet to test the program widely. Over 116 million households are supposed to use in 2020, a major rollout for any tech project. There are concerns it won’t work or that the data could be stolen, especially after the recent Equifax hack put the personal information of 143 million Americans at risk.

In the past, the Census Bureau mailed forms to homes. If people didn’t return the forms, the census would send someone to knock on the door up to six times. A lack of funding could reduce how many times the door knocking happens, experts say.

But Ross insists the census will be thorough. He says census works will still knock on doors multiple times in 2020 and that an “extensive media campaign” will be done.

“It is unfortunate the (NAACP) brought this action. If their true concerns are related to undercounting, there are many non-litigious avenues to communicate and engage on those concerns,” Ross said.