Wage determination integrates supply-side factors (human capital, preferences, labor supply elasticity), demand-side factors (marginal productivity, product market conditions, technology), and institutional factors (unions, minimum wages, norms, regulations) to explain both the level and distribution of wages. In the perfectly competitive model, wages equal the marginal revenue product of labor. In practice, wages are also shaped by bargaining power (rent-sharing between firms and workers), efficiency wage considerations (firms paying above market-clearing wages to elicit effort or reduce turnover), compensating differentials, discrimination, and institutional constraints. Understanding wage determination requires recognizing that no single model captures all the forces at work — the competitive model is the baseline, but departures from it are empirically important.
Understanding why people earn what they earn is one of the central questions of labor economics — and it turns out to be considerably more complex than any single theory can capture. The competitive model provides the foundation: wages reflect marginal productivity. But layered on top are human capital differences, compensating differentials, bargaining dynamics, institutional constraints, and persistent anomalies that collectively determine the wage structure.
The competitive baseline predicts that in equilibrium, workers with identical skills receive identical wages across firms and that each worker is paid their marginal revenue product. This strong prediction serves as a useful benchmark precisely because its failures are informative. The observation that identical workers earn different wages at different firms (the firm wage premium) indicates that something beyond marginal productivity is at work. AKM (Abowd, Kramarz, and Margolis) decompositions of matched employer-employee data show that a substantial fraction of wage variation is explained by firm fixed effects — where you work matters, controlling for who you are.
Rent-sharing provides one explanation for firm wage premiums. Firms in profitable industries or with market power earn rents (profits above the competitive level), and workers capture some of these rents through bargaining. The division depends on relative bargaining power, which is influenced by unionization, outside options, firm-specific human capital, and labor market tightness. A worker at a highly profitable firm earns more than an identically skilled worker at a marginal firm — not because they are more productive but because they share in the firm's rents.
Efficiency wages represent another departure from the competitive model. Shapiro and Stiglitz's shirking model shows that when firms cannot perfectly monitor effort, paying above-market wages gives workers something to lose if caught shirking, providing a self-enforcing incentive mechanism. Akerlof's gift exchange model suggests that workers reciprocate above-market wages with above-minimum effort — a social norm rather than a self-interested calculation. Both models predict involuntary unemployment as an equilibrium outcome: firms do not lower wages to market-clearing levels because the resulting productivity loss would exceed the wage savings.
The institutional dimension — minimum wages, unions, pay regulations, social norms — adds further complexity. Minimum wages set a floor that compresses the bottom of the wage distribution. Unions typically raise wages for their members by 10-20% (the union wage premium) while potentially reducing wages for comparable non-union workers through spillover effects. Pay transparency norms, internal equity policies, and social expectations about "fair" wages create rigidities that prevent wages from adjusting to market-clearing levels. The interaction of these institutional forces with competitive pressures produces the observed wage structure — a distribution that reflects ability, human capital, bargaining power, institutional constraints, and discrimination in proportions that vary across labor markets, industries, and countries.