In the United States, data on wealth distribution is most commonly collected through surveys carried out by the U.S. Census Bureau, most prominently the American Community Survey. Population data on income and wealth is also collected through the Survey of Consumer Finances, undertaken by the U.S. Federal Reserve Board of Governors.
As of 2015, the U.S. Census Bureau carries out several broad national population surveys. The longform census, recorded by the government since 1790, is the most comprehensive. The bureau records several other surveys used for further demographic and specific population research, notably the American Community Survey that reaches around 3.5 million homes per year. These surveys are a major source of information on American income, and are primarily used in data compilation for government use, as most of the data is not made public immediately.
The U.S. Federal Reserve also records a survey on private income and wealth called the Survey of Consumer Finances. The acquired data includes estimates of national median incomes for various socioeconomic levels, and degrees of wealth in incomes. The SCF data is partially available for public consumption, so it is often found cited in private research such as Pew Center reports on income inequality.
Income and wealth data is recorded on a less standardized basis outside of government oversight also. Private research often uses its own sets of surveys in an attempt to capture a representative sample of the population. The resulting data, while potentially not as accurate, is a common source of cited income distribution data in academic papers and research releases.