article:
"Understanding Low Wage Work in the United States"
by Heather Boushey, Shawn Fremstad, Rachel Gragg, and Margy Waller (March 2007)
http://kms1.isn.ethz.ch/serviceengine/Files/ISN/57210/ipublicationdocument_singledocument/78A9433F-FF7F-43D6-BC1B-9778E5B09907/en/lowwagework.pdf