The theory that education can signal worker ability rather than directly raise productivity is signaling theory.
Michael Spence developed the classic job-market signaling model in his 1973 paper “Job Market Signaling.” Employers cannot directly observe an applicant’s underlying ability before hiring, while applicants know more about themselves. Education can help reveal that hidden difference if obtaining credentials is less costly, or less difficult, for higher-ability people. Employers then use educational attainment as evidence when setting wages or making hiring decisions.
In this model, education need not make workers more productive for the credential to influence labor-market outcomes. Its value comes from reducing information asymmetry. This contrasts with human capital theory, which emphasizes skills, knowledge, and productivity gained through schooling. In reality, education can perform both functions: classrooms may build skills while degrees also provide information about persistence, ability, or likely performance.
A related concept is the “sheepskin effect,” in which completing a degree can produce a larger payoff than the additional coursework alone would suggest. Signaling is also distinct from screening: signaling is information sent by the informed party, while screening is an information-gathering method used by the less-informed party.