Polling information from a database such as Polling the Nation.
CBS News. April 15, 2015. "Do you favor or oppose the death penalty for persons convicted of murder?". New York: CBS News. Retrieved on July 1, 2015 (http://poll.orspub.com/document.php?id=quest15.out_1490&type=hitlist&num=12)
A data set from the Inter-university Consortium for Political and Social Research (ICPSR).
U.S. Bureau of Labor Statistics. 2015. Consumer Expenditure Survey 2013-2014. ICPSR36170-v1. Ann Arbor, MI: Inter-university Consortium for Political and Social Research. Retrieved August 21, 2015 (http://doi.org/10.3886/ICPSR36170.v1)
