Before you read this, you need to download the accounting spreadsheet from IRS: IRS Accounting Spreadsheet You want to click on the "2010" link as that is the most current data. After you download the XLS file, open it and see the Table 29 "Collections, Costs, Personnel, and U.S. Population, Fiscal Years 1980 - 2010". For each 5 year span marked in the table: 1980 - 1984: 24% increase in tax 30% increase in IRS cost ($998M) 4% increase in population 1985 - 1989: 27% increase in tax 31% increase in IRS cost ($1.597B) 4% increase in population 1990 - 1994: 17% increase in tax 25% increase in IRS cost ($1.804B) 5% increase in population 1995 - 1999: 28% increase in tax 11% increase in IRS cost ($879M) 5% increase in population 2000 - 2004: 4% decrease in tax 15% increase in IRS cost ($1.497B) 4% increase in population 2005 - 2010: 3% increase in tax 16% increase in IRS cost ($1.955B) 4% increase in populatio