Statistical data can be useful when forming a strong argument, but finding the statistics you need/want is not always straight forward.
Finding the right statistics often means digging through websites and reports.
It takes time, but it is worth it!
American FactFinder provides access to data about the United States, Puerto Rico and the Island Areas. The data in American FactFinder come from several censuses and surveys.
Historical Statistics of the United States: pt. 1 & 2
This includes more than 12,500 time series, mostly annual, providing a statistical history of U.S. social, economic, political, and geographic development during periods from 1610 to 1970.
National Center for Education Statistics: Fast Facts
The purpose of the Fast Facts website is to provide users with concise information on a range of educational issues, from early childhood to adult learning. Fast Facts draw from various published sources and are updated as new data become available.
Statistical Abstract of the United States
The Statistical Abstract of the United States, published from 1878 to 2012, is the authoritative and comprehensive summary of statistics on the social, political, and economic organization of the United States. These sources of data include the U.S. Census Bureau, Bureau of Labor Statistics, Bureau of Economic Analysis, and many other Federal agencies and private organizations.