New numbers from the U.S. Census Bureau on Thursday did nothing to clear up a mystery surrounding just how many people live inside the Lawrence city limits.

The Census’ latest report estimates Lawrence had a population of 88,727 people on July 1, 2011 — or about 4,000 fewer people than city planners estimate live in the city.

Thursday’s report wasn’t expected to solve the mystery. To do that, city leaders will have to formally challenge the Census Bureau’s count taken in 2010. City planning director Scott McCullough said his office likely will file an appeal by late August, but the process is complicated.

“We can’t just tell them that we’ve counted more people than they did,” McCullough said.

Instead, city planners are basing their appeal on the idea that Census Bureau officials did not have an accurate listing of all the housing units in the city limits.

The issue has become about more than just a number. Census totals are used in drawing federal and state boundaries for congressional and legislative districts. The totals also are important in distributing federal dollars to communities. Increasingly, they’ve also become important for local planning efforts.

Here’s perhaps the largest example: City commissioners are studying when to build a $54 million sewer treatment plant south of the Wakarusa River. A new City Hall report says the plant needs to be online by the time the city’s population reaches 105,000 people.

But counted by whom?

Using the city’s estimates, Lawrence will reach the 105,000 population mark in six years, meaning the city needs to begin design work right away. But if the city continues growing at the pace the Census Bureau reports, it will take 18 years for the city to hit the 105,000 mark.

City Manager David Corliss said figuring out the population total is a priority. He said if the city waits too long to build the sewer plant it could slow future growth by creating a time period when the city doesn’t have the capacity to add new homes or businesses. But if the city builds the plant too soon, it would have an expensive piece of infrastructure in place well before there are enough ratepayers to pay for it.

“It is important for us to get a number and settle on it,” Corliss said. “But it is important that we get the right number.”

The report estimates Lawrence’s population grew by 1,084 people since the 2010 Census, for an annual growth rate of 0.98 percent. That’s in line with the growth rate the 2010 Census found for the community, but is still well below the 2 percent rate that was common in the 1980s and 1990s.

Thursday’s Census report provided population estimates for all U.S. cities. Here’s a look at the population and annual growth rates of several other area cities:

• Eudora: 6,217 people, up 1.0 percent

• Baldwin City: 4,569, up 0.9 percent

• Lecompton: 632, up 0.8 percent

• Olathe: 127,907, up 1.2 percent

• Manhattan: 53,678, up 2.1 percent

• Tonganoxie: 5,065, up 1.1 percent

• Topeka: 128,188, up 0.4 percent

• Shawnee: 63,219, up 1.2 percent

• De Soto: 5,813, up 1.3 percent

• Basehor: 4,692, up 1.3 percent

• Ottawa: 12,620, down 0.1 percent

• Kansas City, Kan.: 146,453, up 0.3 percent

• Wichita: 384,445, up 0.4 percent