Social Security is an example of majoritarian politics. It was decided by a relatively small group of people, and it has affected a large and ever growing population, for better or worse.
Majoritarian politics is a system wherein a comparatively small group of people make a decision affecting a large group of people, with the decision affecting the majority, and where the input of the majority is not gathered prior to a decision. Because of the economic state of the 1930s, Congress and the president came together to work out an economic stimulus that would allow a worker to save money to be used at retirement.
The economic state of the country made finding a solution an urgent necessity, so the movement to pass the Social Security Act went into high gear. Political scholars and economic experts attest that some things were not completely thought out in the haste to get the act passed, such as its long-term outlook when the population grew. There were few safeguards put in place on the fund created by the incoming Social Security tax to prevent Congress from borrowing money from it.
As both population has grown and money has been borrowed from the Social Security fund, motions have been put in place to change how the system works in order to address these issues, as the amount coming into the fund has been outpaced by those collecting from the fund.