Union wage rules in the U.S. automobile industry from 1970 to 1999 show consistent patterns despite changes in profits. The study found that wage provisions in union contracts remained stable over time, even after shifts in industry conditions. This suggests that certain wage rules persisted across bargaining rounds, with a return to previous patterns in the mid-1980s. The findings have implications for understanding how unions determine wages and how this affects the overall wage structure in the industry.