How does the Social Security system work?

In almost every financial situation that we deal with on a regular basis, there is the idea of an "account". For example, when you put money into a bank, it is understood to be "your money" and it goes into an account with your name on it. The same thing happens when you contribute to your 401(k) plan at work -- you have an account with your money in it, and if you change employers the money in the account is yours. You also have accounts for your credit card, mortgage, car loan, and so on. In any of these accounts, you add money to the account and take money out of it, and whomever holds the account keeps track of how much you have or you owe.

The Social Security system is nothing like that. In the Social Security system, the money you pay into the system gets immediately paid back out to the people who are currently getting Social Security checks. This arrangement came into being because of the way the system started. In 1935, when Roosevelt signed the Social Security Act into law, there were a lot of people who needed benefits (because of the Great Depression), but there was no money to pay those benefits with. The idea at the time was that people currently working would pay into the system, and their money would immediately go back out in the form of benefit checks. Each generation of retiring workers would get paid by the people currently working, and therefore the system would fund itself forever despite the fact that the system had no money to start with.

This clever idea worked great in 1935 (and for many years after that), but it is going to have a problem in the future for two reasons:

In 1935, there were many more people paying into the system than those receiving benefits. The ratio of workers to retirees meant that workers did not have to pay much into the system in 1935 to support the retirees (this table shows that up through 1950, only 2% of income (1% employee, 1% employer) was withheld for Social Security, compared to 15.30% (7.65% employee, 7.65% employer) today). In the future, the retirement of millions of baby boomers will hurt the ratio -- there will be so many retired people that the working people will not be able to support them. If the population had grown steadily this would not have been a problem, but there is no good way for the design of the Social Security System to handle a population spike like the baby boomers.
Many people have become so used to the idea of a 401(k) plan (where your money belongs to you and grows to a large sum over time through investment compounding), that the idea behind the Social Security system becomes hard to swallow. Currently a worker pays 7.65% of his or her gross income into the Social Security system (with a cap at a gross income of around $70,000), and the employer pays another 7.65% for the worker as well. If you could take that 15.30% of gross income and invest it in a 401(k) plan for the same period of time, it would generate an immense sum of money based on historical returns -- far more than a person with average income (or greater) would get from Social Security. A retiree's Social Security benefit is calculated using a complex formula rather than an account balance, because there is no "account" in the traditional sense.

You might have heard that the Social Security system currently takes in more money than it pays out in order to try to handle the baby boomer problem. What happens with the excess money the system collects? The Social Security system buys U.S. Treasury bonds with the surplus. Essentially, the government (in the form of the Social Security Administration) loans the surplus to itself.

In future decades, when it comes time to start drawing on the collected surplus, the government will pay itself back through tax revenue (or additional borrowing). The Social Security system will start cashing in the bonds, and the government will have to make good on them with tax revenue. That sounds weird because it is weird -- Whether or not it will work is a source of significant debate right now. The effect it will have is that it will shift the payment of Social Security benefits over to the government as a whole. The government as a whole, rather than the Social Security system, will have to repay the treasury bonds that the Social Security system will be cashing in. It will certainly be interesting to see what happens!

Here are several interesting links:

SS FAQ
SS History
Nine misconceptions about social security - this article generated lots of debate.
Social Security Privatization - Privatization proposals also cause debate
Social Security Calculator -- talks about the formula used to calculate your SS benefit once you retire.
5 Reason You Might Need to Visit the Social Security Office