In general, represents the sum of standard and itemized deductions from AGI to compute "taxable income" (the tax base for the regular income tax), but also includes deductions in excess of AGI that could not be used in the computation. Deductions erroneously reported on returns with no AGI were excluded from the deduction statistics. Also Includes "additional" standard deductions for age 65 or over or for blindness (for changes in the standard deduction and its relation to the zero bracket amount, see Statistics of Income-Individual Income Tax Returns, for appropriate years). Total itemized deductions are after statutory limitation.
For additional information about the return filing requirements, see the annual reports, Statistics of Income-Individual Income Tax Returns at https://www.irs.gov/uac/soi-tax-stats-historical-data-tables.
U.S. Department of the Treasury. Internal Revenue Service, Individual Income Tax Filing: Total Deductions [DDMT], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/DDMT, May 24, 2019.