Beginning 2004:Q1, level from FR Board, CM, based on data available by subscription from Mergent on short-term municipal bonds outstanding. Unadjusted flow is the change in the level; seasonally adjusted flow is obtained using X-12-ARIMA procedure. Prior to 2004:Q1, unadjusted flow from a proprietary Thomson Reuters' database, short-term (less than 13 months) municipal securities.