This report presents social and economic statistics for the population of the United States below the low-income level in 1971, based on the March 1972 Current Population Survey. Included are data on selected characteristics of the population below the low-income level in 1971, such as geographic distribution, race and ethnic origin, family status, size of family, education, employment status, work experience, occupation, income (including type and source), and income deficit. Several historical tables detailing a picture of the changing composition of the population below and above the low-income level since 1959, the first year for which low-income data are available, are also presented. A description of the population below the low-income level in 1971 and some analysis of changes in the composition of this population over the past year and since 1959 are included. Families and unrelated individuals are classified as being above or below the low-income level, using the poverty index adopted by a Federal Interagency Committee in 1969. This index centers around the Department of Agriculture's Economy Food Plan and reflects the different consumption requirements of families based on family size, sex, and age of the family head, the number of children, and farm-nonfarm residence. (Author/JM)