Information needed to administer the OASDI program resides on SSA's Master Beneficiary Record (MBR) file. In particular, the file includes data used to determine program eligibility and benefit amounts. In December 2001, the MBR contained records for approximately 46 million individuals who were entitled to receive an OASDI benefit for that month.

The OASDI Public-Use Microdata File contains an extract of data fields from the MBR and consists of a 1 percent random, representative sample of persons entitled to receive an OASDI benefit payment for December 2001. Records on the underlying file for persons entitled to receive an OASDI benefit payment for December 2001 were ordered by state, by sex within state, by age within sex, and by type of benefit within age; a systematic 1 percent random sample was then selected. The file contains approximately 460,000 records with 16 data fields on each record, and is available in a standard SAS file structure as well as the CSV file format.

Since the sample for the OASDI Public-Use Microdata File is a representative 1 percent systematic random sample of persons entitled to receive an OASDI benefit payment for December 2001, all records have weight equal to 100. Variance and standard errors can be approximated with the standard formulas used for simple random sampling.

Descriptions of data fields are provided in the Data Dictionary for this file. The descriptions cover the content of each field, the method of presentation, and the disclosure avoidance steps taken to provide confidentiality. Because information on the internal MBR record file is used to administer the OASDI program, data quality is extremely high because data are validated and kept current. Note that the information on each file refers to a single time period—December 2001.

Individual identifiers have been removed from all records on this file, and other distinguishing characteristics have been modified to prevent identification of persons to whom a record pertains. Records are sequenced in random order.

Topcodes and bottomcodes are employed for all numeric fields to avoid showing extreme field values on a data record. Values beyond the topcode or bottomcode are replaced by the average of the values in excess of the respective topcode or bottomcode. Topcode and bottomcode values were derived at the national level, and the replacement values are also based on national estimates for this file. Values shown for categorical fields are groupings of detailed information from the internal file and numeric variables are rounded to the nearest $5. All topcode and bottomcode values, replacement values, and information on detail groupings are provided to users as part of the file documentation.