Pay Gap Adjusted vs Non-Adjusted(Wiki)
Adjusting for different causes
Comparing salary "within, rather than across" data sets helps to focus on a specific factor, by controlling for other factors. For example, to eliminate the role of horizontal and vertical segregation in the gender pay gap, salary can be compared by gender within a specific job function. To eliminate transnational differences in the job market, measurements can focus on a single geographic area instead.[29]
Reasons
The non-adjusted gender pay gap is not itself a measure of discrimination. Rather, it combines differences in the average pay of women and men to serve as a barometer of comparison. Differences in pay are caused by occupational segregation (with more men in higher paid industries and women in lower paid industries), vertical segregation (fewer women in senior, and hence better paying positions), ineffective equal pay legislation, women's overall paid working hours, and barriers to entry into the labor market (such as education level and single parenting rate).[30]
Some variables that help explain the non-adjusted gender pay gap include economic activity, working time, and job tenure.[30] Gender-specific factors, including gender differences in qualifications and discrimination, overall wage structure, and the differences in remuneration across industry sectors all influence the gender pay gap.[31]
https://en.wikipedia.org/wiki/Gender_pay_gap#Adjusting_for_different_causes