"The congressional franking privilege allows Members of Congress to send official mail via the U.S. Postal Service at government expense. This report provides information and analysis on the costs of franked mail in the House of Representatives and Senate. In FY2013, total expenditures on official mail were $7.6 million. House official mail costs ($6.2 million) were 82% of the total, whereas Senate official mail costs ($1.4 million) were 18% of the total. In FY2012, total expenditures on official mail were $24.8 million. House official mail costs ($23.3 million) were 94% of the total, whereas Senate official mail costs ($1.5 million) were 6% of the total These expenditures continue an historical pattern of Congress spending less on official mail costs during non-election years than during election-years (Figure 3). However, analysis of monthly data on official mail costs indicates that, due to the structure of the fiscal year calendar, comparisons of election year and non-election year mailing data tend to overstate the effect of pre-election increases in mail costs, because they also capture the effect of a large spike in mail costs from December of the previous calendar year. The analysis demonstrates that between FY2000 and FY2013, higher official mail costs in evennumbered fiscal years occurred for two reasons: a general increase in monthly mail costs prior to the pre-election prohibited period, and a significant spike in costs during December of oddnumbered years. Both increases were largely the result of an increase in the number of House Members sending mass mailings during those months."
CRS Report for Congress, RL34188