Lesson preview · Signaling Screening
Signaling
~6 min · Free to read
Signaling is an action taken by the informed party to credibly reveal their type to the uninformed party. Michael Spence’s groundbreaking insight (1973): education may function primarily as a signal of ability rather than a source of human capital. If high-ability workers find education less costly to obtain (in effort, not just money), then choosing a costly education level can credibly separate high types from low types.
Key Term
Signaling (Spence Model)
A signal must be costly and differentially costly — it must cost more for the low-quality type to produce than the high-quality type. If education were equally easy for everyone, low-ability workers would mimic high-ability workers and the signal would be worthless. The signal works precisely because it is too expensive for low types to fake.
For a separating equilibrium to hold, two conditions must be met: (1) High types find it worthwhile to signal — the wage premium from signaling exceeds their cost of education. (2) Low types find it NOT worthwhile — the wage premium is less than their cost of education. The employer then rationally offers a high wage to those with the signal and a low wage to those without. Both types self-select optimally, and the information asymmetry is resolved.
The wage gap must exceed the high type’s signaling cost but fall short of the low type’s cost. This ensures only high types signal.
Worked Example
Employers offer dollars to workers with a degree and dollars to workers without. A degree costs a high-ability worker 30,000 dollars in effort and a low-ability worker 50,000 dollars in effort. Does a separating equilibrium exist?
The widget below uses the worked example’s numbers. The degree costs a high-ability worker 30,000 dollars in effort and a low-ability worker 50,000 dollars. The no-degree wage is 40,000 dollars. We’ll step through three values for the with-degree wage — 60,000, 80,000, then 100,000 dollars — and watch how the wage premium changes each type’s incentive.
The left panel shows the high-ability worker’s net pay under “get the degree” versus “skip it.” The right panel shows the same comparison for the low-ability worker. In each panel the taller bar is highlighted — that’s what a rational worker picks. A separating equilibrium requires the high type to pick the degree and the low type to skip; if both make the same choice, we get pooling instead.
Check yourself · no marks
In the Spence model, does education need to actually increase productivity for the signal to work?
Commit to one first. Guessing and being wrong beats reading the answer cold.
Practice · 1 / 4
For education to work as a signal, it must be:
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