Since its inception, Social Security has featured a taxable maximum (or “tax max”). In 1937, payroll taxes applied to the first $3,000 in earnings. In 2011, payroll taxes apply to the first $106,800 in earnings. This policy brief summarizes the changes that have occurred to the tax max and to earnings patterns over this period. From 1937 to 1975, Congress increased the tax max on an ad-hoc basis. Increases were justified by the desire to improve system financing and maintain meaningful benefits for middle and higher earners. Since 1975, the tax max has generally increased at the same rate as average wages each year. Some policymakers propose increasing the tax max beyond wage-indexed levels to help restore financial balance and to reflect growing earnings inequality, as workers earning more than the tax max have experienced higher earnings growth rates than other workers in recent decades.