In certain circumstances, a working single parent in Chicago would be foolish to take a pay raise to $18 an hour from $12 an hour. They’d fall from the top of the welfare cliff and see a drastic net reduction in benefits, leaving them with as much as one-third less in household resources. This loss would only be made up again by finding a job paying $38 an hour.

http://www.illinoispolicy.org/illinois-warped-welfare-system-traps-families-in-poverty/