Estimates rely on government data which can be inaccurate. Overall we believe the estimates to be lower bounds due to missing data in federal data sets. In cases where we know the omissions are significant, such as subsidy estimates for risk transfers, we will note that an estimate is 'unknown' in the form of a question mark. Per household figure is calculated using data from the March 2009 Current Population Survey
. Estimates calculated as of September 2010.