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999999 = N.I.U. (Not in Universe).

The Census Bureau applies different disclosure avoidance measures across time for individuals with high income in this variable. Detailed explanations of these methods, topcodes, and replacement value and swap value thresholds are available here.


INCSSI indicates how much pre-tax income (if any) the respondent received from Supplemental Security Income (SSI) during the previous calendar year.

Amounts are expressed as they were reported to the interviewer; users must adjust for inflation using Consumer Price Index adjustment factors.


Apart from the effect of inflation, this variable is largely consistent over time. From 1976 to 1994, respondents reported a single figure for the year. Beginning in 1995, respondents could report amounts for smaller time intervals, such as weekly, bi-weekly, twice monthly, or monthly, along with the number of payments.

For 1962-1967, the value of income from SSI is subsumed in the INCUNERN variable, which encompasses all income from sources other than wages and salaries (INCWAGE), non-farm businesses (INCBUS), and farms (INCFARM).

For 1968-1975, the value of SSI payments would be included in the INCWELFR variable, on income from welfare or public assistance.

Comparability with IPUMS-USA

INCSSI in IPUMS-CPS is comparable to the INCSUPP variable that was first available in census 2000 in IPUMS-USA. Summing the values for INCWELFR and INCSUPP in IPUMS-USA and the values for INCWELFR and INCSSI provides general comparability between the two databases for the period from 1968 forward, if appropriate adjustments are made for inflation and universe differences.


  • 1976-1979: Persons age 14+.
  • 1980+: Persons age 15+.


Years Jan Feb ASEC Apr May Jun Jul Aug Sep Oct Nov Dec
1976 – 2023 - - X - - - - - - - - -