The federal government agrees it undercounted Bluffton's population after the town challenged the results of the 2010 Census.
It remains to be seen how much the adjustment by the U.S. Census Bureau will pay off for Bluffton.
The agency acknowledged in a Dec. 21 letter that it missed some residents and has raised the town's population as of April 1 to 12,893 -- a gain of 363 people.
However, Bluffton's mayor believes the number is still too low.
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"At the end of the day, I think we are at 15,000, but we have got to take the numbers they have given us," Lisa Sulka said.
Census data are key factors in determining how much state and federal funding communities receive, town manager Anthony Barrett said. As of last year, Bluffton received $18.45 per person in state aid. The town won't retroactively qualify for money based on the revised count.
"Our research found errors in the geographic placement of housing units/group quarters related to the town of Bluffton," Census Bureau acting director Thomas Mesenbourg wrote in the letter announcing the revision.
Based on pre-2010 Census data, the Buck Island and Simmonsville roads annexation study and new residential trash service, the town estimates the current population is 15,400.
"You can readily understand how a miscount one way or the other could occur by looking at a map which depicts our corporate boundaries: Unincorporated Beaufort County and the town share the zip code," Barrett wrote in an email.
He, too, says the 2010 count is inaccurate, but by how much is "anyone's guess."
Bluffton was one of the fastest growing towns in South Carolina before the recession, adding more than 11,000 people between 2000 and 2010. Those gains were made through annexation and a sharp increase in housing construction.
The town paid for a special census in 2005 that found 4,885 residents. Three years later, after a census estimate showed only 4,312 residents, Bluffton challenged and won, resulting in an increase to 12,333.
With so much at stake, Sulka and Barrett indicated another special mid-decade census is possible.
"When we did it in 2005, it made sense for us," she said. "If it makes sense to do it again, at that time, we will consider all of the options."
Follow reporter Casey Conley at twitter.com/IPBG_Casey.