The SIPP is a household-based survey designed as a continuous series of national panels. Each panel features a nationally representative sample interviewed over a multi-year period lasting approximately four years. SIPP is a source of data for a variety of topics and provides for the integration of information for separate topics to form a single, unified database. This allows for the examination of the interaction between tax, transfer, and other government and private policies. Government policy formulators depend heavily upon SIPP for information on the distribution of income and the success of government assistance programs. SIPP collects information for assistance received either directly as money or indirectly as in-kind benefits. SIPP data provide the most extensive information available on how the nation’s economic well-being changes over time, which has been SIPP’s defining characteristic since its inception in 1983.