Governments provide such a preponderance of social statistics, that it's often important to remember that there are certain types of data you won't find in government statistics, at least in the United States. Some common examples to watch out for:
- Religion: Some older censuses (19th century) asked religious affiliation, and you can sometimes find statistics on numbers of churches. Other than that you’ll need to rely on non-government sources. Some government statistical compilations will report religion statistics gathered by other sources.
- Voting: The United States employs a secret ballot. The federal and state governments have statistics on what votes were cast (by precinct, county, or state), plus demographic statistics about registered voters, but nothing that links the two. Exit polls are generally the only source for voting statistics by race, age, sex, or other factors.
- Detailed Household Expenditures: The government tracks how much families spend on big categories like food, rent, and entertainment, but they don’t track how much families spend on meat, curtains, home videos, or individual brand names. Use commercial market research reports for detailed spending data.
- Product Sales: Unless it crosses the border (see US Foreign Trade), the government rarely keeps records on the manufacture, transport, or sale of individual products. Some statistics are available for primary resource production (agriculture, fisheries, forestry, and mines) and sales by industry. Otherwise, use commercial market research reports for detailed sales data.
- Microdata: Though governments collect vast amounts of data, because of privacy laws most of it is published only as aggregate data, i.e. summary tables which don’t reveal anything about the individual people or businesses. The major exceptions are SEC reports for publicly traded companies, campaign finance reports, the Census Public Use Microdata Samples (PUMS), and the census schedules (the original forms released seventy-two years after the census is over).