This new revenue stream applied ordinary federal income tax on 50% of single filers' or couples' Social Security benefits if they respectively earned more than $25,000 or $32,000 in adjusted gross income (AGI). A second tier was added in 1993 under the Clinton administration that allowed 85% of Social Security benefits to be taxed if a single filer earned above $34,000 in AGI, or over $44,000 for couples filing jointly. The Consumer Price index for Urban Wage Earners and Clerical Workers, or CPI-W, is the inflationary tether that determines Social Security's annual COLA.