Introduction to Human Capital
Human Capital Theory, pioneered by Gary Becker and Theodore Schultz, postulates that individuals invest in themselves through education, training, and health, much like a firm invests in physical capital. These investments increase the worker’s marginal product of labor (MPL), thereby commanding a higher wage in the labor market.
The Mincer Wage Equation
The empirical foundation of human capital theory is the Mincer equation (Jacob Mincer, 1974), which estimates the logarithmic earnings as a function of schooling and experience.
$$ \ln(w) = \beta_0 + \rho S + \beta_1 X + \beta_2 X^2 + \epsilon $$
Where:
- $\ln(w)$ is the natural logarithm of earnings.
- $S$ is years of schooling.
- $\rho$ represents the rate of return to an additional year of schooling.
- $X$ is years of potential labor market experience.
- $X^2$ captures the concave nature of earnings over a lifetime (earnings rise with experience but at a decreasing rate).
Signaling vs. Human Capital
A major competing theory is the Signaling Model (Michael Spence). Signaling suggests that education does not intrinsically make workers more productive. Instead, degrees act as an expensive signal to employers about the worker’s preexisting innate ability and grit, sorting high-ability from low-ability individuals.