One reason is that the traditional safety net plans such as Social Security are usually funded on a “pay as you go” basis, meaning that the taxes paid by people working now support the benefits to those retired. That system is being threatened by two demographic trends. The first is that people are living longer, which means they collect benefits for more years. The second is that people are having fewer children, so the ratio of workers to retirees is falling, threatening the viability of the system.
