The census is a massive undertaking aimed at counting every resident of the United States and collecting information about demographics.

Residents have a vested interest in being counted because the information is used to determine political representation through the redrawing of legislative districts. Those population numbers are used to divide up $675 billion in federal government funding, and state funding as well.

If people go uncounted, their communities could receive less money and services than they should, possibly for a decade.

In between decennial censuses the government estimates population changes. South Carolina's state-shared revenue and local option sales tax money, and federal funding for Medicaid, road construction, housing, food stamps and other programs are based on the detailed counts conducted every 10 years.

Here are key dates in 2020 for the census:

January 2020: The Census Bureau begins counting, starting with the population in remote Alaska. Hundreds of thousands of temporary census takers are being hired (visit 2020census.gov/jobs).

April 1, 2020: It's Census Day, because the census will count where people live on this date. By April 1, every home should receive an invitation to participate in the 2020 census online, by mail or by phone.

April 2020: Census takers begin visiting college students who live on campus, people living in senior centers, and others who live among large groups of people.

May 2020: The Census Bureau begins visiting homes that haven't responded to the 2020 census to make sure everyone is counted.

December 2020: The Census Bureau delivers apportionment counts to the president and Congress as required by law.

March 31, 2021: By this date, the Census Bureau will send redistricting counts to states. That information is used to redraw legislative districts based on population changes.

Undercounting is always an issue when the census is conducted. The 2000 census was estimated to have undercounted the population of South Carolina by about 48,000 people, costing the state about $60 million in federal funding over a decade.

Charleston County officials said the county's population was under-counted in 2000 by more more than 9,000 people, costing the county hundreds of thousands of dollars. Fast-growing Mount Pleasant spent $787,717 in the mid-2000s to conduct a special census to prove how much the town had grown, and collected about $3 million in additional revenue as a result.

In 2010, Charleston Mayor Joe Riley went door to door to urge college students in the city to make sure they were counted, and Isle of Palms erected signs and billboards to encourage census participation. South Carolina gained a seat in Congress, from six to seven, following the 2010 Census.

In the 2010 Census, the black and Hispanic populations were undercounted nationally, and the non-Hispanic white population was overcounted, a Census Bureau report concluded in 2012. Undercounts of particular age groups, such as children or the elderly, could impact funding for programs that particularly benefits those age groups, such as schools or senior services.

For 2020, the Palmetto State created the South Carolina 2020 Complete Count Committee, with 55 organizations and government agencies participating.

An accurate count in 2020 will be particularly important for South Carolina's rural counties, which are expected to lose substantial state funding because the state's population has shifted to urban and coastal counties. Rural counties could lose even more if residents there aren't all counted.