At least 10% of the nation’s counties have exceeded their 2000 Census mail participation rates by at least five percentage points, according to a new analysis of 2010 Census response by the Center for Urban Research at the City University of New York Graduate Center. The analysis is based on Census Bureau participation rate data as of April 13.

The analysis also turned up the intriguing pattern that in the nation’s largest cities, the neighborhoods that have surpassed their 2000 participation rates also tend to have high “hard-to-count” scores, meaning that they had housing, demographic and socioeconomic variables correlated with poor response in the 2000 Census. The analysis suggested that this finding could reflect the intensive outreach and advertising campaigns aimed at these areas, or it could reflect their changing demographic characteristics.

Earlier this week, the Census Bureau noted that four states had surpassed their 2000 participation rates. Bureau officials have set a deadline of April 16 for households to mail back their forms in order not to be put on the list for a follow-up visit from a census-taker.