The term "glass ceiling" as a discriminatory barrier limiting females from reaching senior management positions was used in the early 1990s, around the time that females first surpassed males in annual university degrees obtained in the United States. Studies of employment in various, such as the 2003 study of employment data in Sweden conducted by Albrecht, Bjӧrklund, and Vroman, have found a consistent gap between men's and women's wages after these are controlled for gender differences in age, education level, education field, sector, industry, and occupation. However, empirical studies as early that of Powell and Butterfield in 1994 have suggested that gender, as a job-irrelevant variable in consideration of promotions to top management positions, may actually work to women's advantage. Whereas the gender gap in pay is strongly supported by data, the glass-ceiling notion itself as a discriminatory force has been harder to account for in empirically proven terms.
     Studies that have been considered by some a partial repudiation of the glass-ceiling theory have indicated that men and women differ in their preferences for competition and that such differences impact economic outcomes. If women are less likely to compete, they are less likely to enter competitive situations and hence likely to win. For example, in a laboratory experiment featuring a non-competitive option and a competitive incentive scheme, men selected the tournament twice as much as did women of equal ability. One explanation is that men are inherently more competitive; another is that the social influences limiting women's presence in executive leadership generally make their impact long before women are near the ceiling.