US Bureau of Labor Statistics Occupational Outlook Handbook:
https://www.bls.gov/ooh/arts-and-design/home.htm
North American Industry Industry Classifications (for researching further):
https://www.bls.gov/ooh/arts-and-design/home.htm
Payscale College Salary Report: Art Majors:
https://www.payscale.com/college-salary-report/common-jobs-for-majors/art
Artist's & graphic designer's market 2016: how to sell your art and make a living
Design Intelligence, volume 18, number 2, 2012 compensation, bonus & benefits survey: