Each PSID family in every year through 2009 (except 1969, for which the addresses are unavailable) has been identified as living in housing units subsidized by the U.S. Department of Housing and Urban Development (HUD), the Farmer’s Home Administration, through tax credits administered by the Department of Treasury, or state housing programs. This was accomplished by matching the addresses of PSID families in each year with those in the Assisted Housing Database (AHD). A description of the AHD can be found in:

Newman, S. and A. Schnare (1997). "...' And a Suitable Living Environment': The Failure of Housing Programs to Deliver on Neighborhood Quality." Housing Policy Debate, #8 (4): 703-741.
  The matching process involved two main components: standardizing the PSID and AHD addresses, and matching the standardized addresses.

As described in the Assisted Housing Match Data Codebook, once all of the matching was completed, the resulting data file identifies whether a PSID address available for a given year corresponded to an assisted housing address, and, if so, the type of assisted housing (e.g., public housing, Low Income Housing Tax Credit, state subsidy). As already noted, PSID addresses for 1969 are unavailable and the address-match data skips 1969. However, for individuals who did not move to a new location in 1969, it is possible to impute their assisted housing status based on their 1968 or 1970 addresses.