Industrial relations researchers have long recognized the importance of bargaining power in understanding wage settlements between labor and management. As an empirical matter it has been a challenge to develop measures of union bargaining power. Using a unique data set from Japan, this study identifies how close contract settlements came to satisfying organized labor’s original demands. With those survey results over the 1960-1999 period, it is possible to develop a measure of union power and distinguish how it has fluctuated over time. These findings for Japan have important implications for empirical analysis of union bargaining power.