The General Educational Development (GED) credential is issued on the basis of an eight hour subject-based test. The test claims to establish equivalence between dropouts and traditional high school graduates, opening the door to college and positions in the labor market. In 2008 alone, almost 500,000 dropouts passed the test, amounting to 12% of all high school credentials issued in that year. This chapter reviews the academic literature on the GED, which finds minimal value of the certificate in terms of labor market outcomes and that only a few individuals successfully use it as a path to obtain post-secondary credentials. Although the GED establishes cognitive equivalence on one measure of scholastic aptitude, recipients still face limited opportunity due to deficits in noncognitive skills such as persistence, motivation and reliability. The literature finds that the GED testing program distorts social statistics on high school completion rates, minority graduation gaps, and sources of wage growth. Recent work demonstrates that, through its availability and low cost, the GED also induces some students to drop out of school.

This is from the abstract of “The GED” by James J. Heckman, John Eric Humphries, and Nicholas S. Mader, NBER Working Paper #16064, June 2010. Screening, anyone?

A few excerpts from the study:

Controlling for their greater scholastic ability, GEDs are equivalent to uncredentialed dropouts in terms of their labor market outcomes and their general performance in society. On average, obtaining a GED does not increase the wages of dropouts. While GEDs go to college at higher rates than dropouts, few finish more than one semester. The same traits that lead them to drop out of school also lead them to leave from jobs early, to divorce more frequently, and to fail in the military.
A primary cause [of growth in the GED program] is the growth of government programs that promote the GED as a quick fix for addressing the high school dropout problem.
None of this would matter if the GED were harmless, like wearing a broken watch and knowing that it is broken. But the GED is not harmless. Treating it as equivalent to a high school degree distorts social statistics and gives false signals that America is making progress when it is not. A substantial part of the measured convergence of black and white high school attainment is fueled by prison-issued GEDs.