The Kitagawa–Blinder–Oaxaca decomposition is a statistical method that explains the difference in the means of a dependent variable between two groups by decomposing the gap into that part that is due to differences in the mean values of the independent variable within the groups, on the one hand, and group differences in the effects of the independent variable, on the other hand.

See the Wikipedia article https://en.wikipedia.org/wiki/Blinder%E2%80%93Oaxaca_decomposition