The Statistical Abstract of the United States is the authoritative and comprehensive summary of statistics on the social, political, and economic conditions of the United States.
Not all periodical publications are created equal. Scholarly publications are peer-reviewed and should be your first choice for accurate and in-depth information. The above link will help you select appropriate periodical sources.
The above link will help you differentiate between primary and secondary resources. You should strive to reference primary resources when making your own inferences on a subject. Secondary sources can be used to compare or contrast your findings.