A decade ago, there were 1,200 challenges filed by cities and counties. Based on feedback so far, the U.S. Conference of Mayors is predicting a big jump in that number. That's because tighter budgets are making local officials more sensitive to drop-offs in federal money for Medicaid and other programs.
Nearly $450 billion in federal aid is distributed to states based on population each year, or roughly $1,500 per person.
Among the cities planning challenges: Detroit, Houston, Miami and New York.
In California, officials estimate the census failed to count 1.25 million people there.
The census already has identified errors involving 26,000 people in six states.
