The 2020 U.S. Census will require $15.6 billion — $3.3 billion more than estimated in 2015 — after a government review found that technological upgrades would be tougher to implement and save less money than previously thought, Commerce Secretary Wilbur Ross told lawmakers today.

The Census Bureau, housed within the Commerce Department, hopes the additional funding will bring the project back on track after years of missed deadlines, incomplete projects and underfunding, Ross said. The new budget would include $1.2 billion for contingencies.

“There are still many challenges ahead, and these additional resources I have described are urgently needed,” Ross said in his testimony to the House Oversight Committee. “An efficient 2020 Census that provides a full, fair and accurate count has been one of my highest priorities since being confirmed in February.”

The decennial count, enshrined in the U.S. Constitution, determines how many members of Congress each state will have while providing a detailed look at the nation’s demographics. Committee members, especially Republicans, expressed concerns about the ability for the agency to meet its new budget and goals. The 2010 Census failed to deliver on a promised digital overhaul in record collection, resulting in some data collected via pen and paper.

Ross said the logistical challenges of organizing the Census has made it “one of the most challenging aspects of the entire Commerce portfolio,” citing the decline in voluntary responses and a deep skepticism of government.

The Census Bureau also manages other data collection efforts, including the American Community Survey, which estimates population and demographic characteristics between every Census. The agency also conducts surveys for economic data such as employment.