Second quarter levels are benchmarked annually to U.S. Census Bureau, Annual Survey of Public Pensions: State & Local Data, Table 1: National Summary of Public-Employee Retirement Systems. Calculated as a proportion of Total Mortgages based on data from a sample of the Comprehensive Annual Financial Reports of the largest state and local governmental units. For quarters more recent than the benchmark, growth rates are estimated using U.S. Census Bureau, Quarterly Survey of Public Pensions. Series is converted to quarterly by interpolation. Unadjusted flow is the change in the level; data for the most recent ten years show no significant seasonality.