This paper examines the relationship between job seniority and wages, finding that wages rise with job tenure. Using longitudinal data from the Panel Study of Income Dynamics (PSID), the author estimates that 10 years of job seniority raises the wage of the typical male worker in the U.S. by over 25 percent. This estimate is a lower bound on the true returns to job seniority, as other factors such as unobserved personal characteristics and job mobility can affect wage growth. The study also finds that the returns to job seniority are similar across different occupational categories, though union workers may experience larger wage losses if displaced from their jobs. The paper highlights the importance of job-specific capital in employment relationships and suggests that the accumulation of such capital is a key factor in life-cycle earnings and productivity. The findings challenge the assumption that wages are primarily determined by general human capital and suggest that job-specific experience plays a significant role in wage growth. The study also notes that the estimated returns to seniority are robust to various sources of bias, including selection effects and measurement errors. Overall, the paper provides strong evidence that wages do rise with job seniority, and that job-specific capital is an important component of employment relationships.This paper examines the relationship between job seniority and wages, finding that wages rise with job tenure. Using longitudinal data from the Panel Study of Income Dynamics (PSID), the author estimates that 10 years of job seniority raises the wage of the typical male worker in the U.S. by over 25 percent. This estimate is a lower bound on the true returns to job seniority, as other factors such as unobserved personal characteristics and job mobility can affect wage growth. The study also finds that the returns to job seniority are similar across different occupational categories, though union workers may experience larger wage losses if displaced from their jobs. The paper highlights the importance of job-specific capital in employment relationships and suggests that the accumulation of such capital is a key factor in life-cycle earnings and productivity. The findings challenge the assumption that wages are primarily determined by general human capital and suggest that job-specific experience plays a significant role in wage growth. The study also notes that the estimated returns to seniority are robust to various sources of bias, including selection effects and measurement errors. Overall, the paper provides strong evidence that wages do rise with job seniority, and that job-specific capital is an important component of employment relationships.