The US federal
Earned Income Tax Credit is a
refundable tax credit that supplements the earnings of low- and moderate-income workers. Enacted in 1975, the EITC was expanded in 1986, 1990, and 1993.
See also:
New Research Findings on the Effects of the Earned Income Tax Credit, Center on Budget and Policy Priorities, March 11, 1998 (
http://www.cbpp.org/311eitc.htm)