When Congress forms a new program whose budget will be determined by eligibility criteria for benefits, such as the Food Stamp Program (FSP), spending for this program becomes mandatory spending. Over the last few decades, the proportion of mandatory, as opposed to discretionary, spending has gradually been increasing. In the 1960s, one-third of the federal budget went toward mandatory spending. Today, this number is closer to two-thirds, with the remaining third available for discretionary programs. The trend that has resulted in a greater portion of the budget going to mandatory spending is largely a result of the increasing size of the national debt, because payment of the interest on that debt falls within mandatory spending.