What is a social security number used for?

A social security number primarily serves as a means of tracking earnings and benefits in the United States. It is crucial for the Social Security Administration to manage an individual's contributions to the Social Security system, which ultimately benefits retirees, disabled individuals, and survivors of deceased workers. The number is used to record earnings for taxation purposes as well, ensuring that the money withheld from paychecks is accurately attributed to the correct individual’s earnings history.

While it might seem that a social security number could assist in tracking academic achievements or military service records, these functions are not its primary purpose. The social security system's main focus is on financial aspects related to employment, benefits eligibility, and retirement planning rather than educational or military documentation. Thus, the correct answer highlights the fundamental role of the social security number in the financial realm.