Gender Pay Gap

[Mara Lange]

I want to calculate the gender pay gap. For this, I use the following command:

egen median_inc_m = median(inc) if (sex==1)
egen median_inc_f = median(inc) if (sex==2)
gen paygap = (median_inc_m - median_inc_f) / median_inc_m * 100

However, the generated variable paygap has zero observations and therefore no value. Where is my error?

[Maarten Buis]

median_income_m contains the medium income for males when the observation is male and missing otherwise. Similarly, medium_income_f contains the medium income for females and missing otherwise. Assuming that there is no observation who is simultaneously male and female, then there is no observation that contains both medians.