Since 1941, the Social Security Administration (SSA) has periodically surveyed the aged to determine their economic status. The first national survey was conducted in 1963. In 1976, SSA's Office of Research and Statistics began compiling a biennial series of reports on the income of the aged based on data collected by the U.S. Census Bureau in its Current Population Survey. These SSA reports are published under the title Income of the Population 55 or Older. The most recent edition of that publication is based on 2000 data, which, along with special tabulations, form the basis for this chartbook. The unit of analysis here, with the exception of measures of poverty, is the "aged unit" and not the household, the family, or unrelated individuals, as are used by the Census Bureau. The aged unit is either a married couple living together, with husband or wife aged 65 or older (generally measured by the age of the husband), or a person 65 or older who does not live with a spouse. The unit of analysis for poverty is persons aged 65 or older.