Generally, you should use library databases to find your articles, and the web to supplement your arguments with statistics, demographic information, and reports. Things to keep in mind when searching the web:
Offers access to data and digital content from the U.S. Census Bureau which includes statistics about population, housing, industry, and business.
This authority for statistics on the social, political, and economic conditions of the U.S. provides a snapshot of America and its people with data from the Census Bureau, Bureau of Labor Statistics, and other Federal agencies and private organizations.