Net worth includes the value of a person's home, possessions and savings accumulated over the years, including stocks, bank accounts, real estate, cars, boats or other property, minus any debt such as mortgages, college loans and credit card bills. Older Americans tend to hold more net worth because they are more likely to have paid off their mortgages and built up more savings from salary, stocks and other investments over time. The median is the midpoint, and thus refers to a typical household.The 47-to-1 wealth gap between old and young is believed by demographers to be the highest ever, even predating government records. In all, 37 percent of younger-age households have a net worth of zero or less, nearly double the share in 1984. But among households headed by a person 65 or older, the percentage in that category has been largely unchanged at 8 percent. While the wealth gap has been widening gradually due to delayed marriage and increases in single parenting among young adults, the housing bust and recession have made it significantly worse. For young adults, the main asset is their home. Their housing wealth dropped 31 percent from 1984, the result of increased debt and falling home values. In contrast, Americans 65 or older were more likely to have bought homes long before the housing boom and thus saw a 57 percent gain in housing wealth even after the bust. Older Americans are staying in jobs longer, while young adults now face the highest unemployment since World War II. As a result, the median income of older-age households since 1967 has grown at four times the rate of those headed by the under-35 age group. Social Security benefits account for 55 percent of the annual income for older-age households, unchanged since 1984. The retirement benefits, which are indexed for inflation, have been a consistent source of income even as safety-net benefits for other groups such as low-income students have failed to keep up with rising costs or begun to fray. The congressional supercommittee that is proposing budget cuts has been reviewing whether to trim college aid programs, such as by restricting eligibility or charging students interest on loans while they are still in school.