I would not put much weight into the census estimates.

Quote taken from this story about Grand Rapids.
http://www.mlive.com/news/grand-rapi...rapids_po.html
The numbers released today for U.S. cities and villages may have little value due to a change in methodology, said Kenneth Darga, state demographer.

“Although these are official estimates from the U.S. Census Bureau and they reflect county-level trends identified from tax returns and other data, they do not reflect data about activity below the county level,” he said. “Thus, they are not suitable for analysis of differences among cities, villages, and townships within counties.”

Census Bureau staff said they took county data on housing units and extrapolated those estimates down to cities within those counties. Because of that, population estimates for cities within the same county grow or decline at the roughly the same rate.