This set of variables (mbr_ssdi_applied_1?mbr_ssdi_applied_4) indicate whether there is a corresponding record of Social Security Disability Insurance (SSDI) application in the Master Benefit Record (MBR). Details for up to four SSDI applications are maintained. If the individual applied more than four times, then details for only a subset of the applications are recorded in this data, with priority given to approved and more recent applications. The first recorded application, the last recorded application, the first recorded application during the SIPP interview period, and the last recorded application during the SIPP interview period are always kept. For example, if a person applied for SSDI three times, this will be reflected in the following way: mbr_ssdi_applied_1 = 1, mbr_ssdi_applied_2 = 1, mbr_ssdi_applied_3 = 1, mbr_ssdi_applied_4 = 0.