Monthly benefit payable to retired or disabled worker under Social Security. It is calculated by using the average monthly earnings of the covered person while working. Under this formula, lower-income workers receive a greater percent of the income they had earned while employed than do more highly paid workers. Benefits for spouse, other dependents, and survivors are figured as a percentage of the PIA. A worker who takes early retirement may receive a portion of the PIA at age 62. The PIA is used to calculate most other benefits.