There was a case recently in the UK where Next (high street clothing chain) were paying their warehouse staff more than their shop staff for (apparently) similar work. The shop workers had a higher proportion of female workers than the warehouse workers (something like 70% vs 50%).
Next claimed this was because the market rate was higher for warehouse workers. They got sued by the female shop workers for discrimination.
They lost and have to pay back pay. Now... you might think 70% vs 50% is barely a difference - did the Next bosses really discriminate? Surely not. Well, that's what the court thought too. Apparently even though they accepted that there was no conscious or unconscious discrimination, the effect of the pay difference was in itself discriminatory.
I dunno how that makes any sense. The shop workers should have sued the IT department and then they'd be in for a serious pay day!