Lyle's comments box can only take 1000 characters, which is simply not enough to challenge the complacent, naive view of a perfect little world of employment where everybody gets jobs on merit.
I know I ought to post links, to 'prove' my arguments, but I'm afraid the most important link is to my brain and some fifteen years experience in this area and a wealth of absorbed knowledge.
To make a decision to hire on ethnicity is illegal. However, in general, most large organisations have a situation where higher up the food chain , the higher the proportion of staff are white able-bodied men. There is no evidence that white able bodied men are, in general, more able to do the job than other people. However, irrelevant factors within the recruitment process may indirectly lead to discrimination. Without measuring , you don't know if you're doing things right.
Eg in general, men will apply for a job if they meet 50% of competencies, whereas women tend to apply if they meet >75% or 90%. Also, in general, men tend to volunteer more for management courses than women (I'm hazier on ethnic differences). Again, specifically on gender, an organisation that finds itself with more women at a low level and more men at a higher level may conclude it's the way of the world, or may find that many very able women (usually with children) are held back, for example, by unnecessarily inflexible working patterns.
And it's not about politically correct stereotypes; if used by intelligent people, such data can be used to encourage and maximise the potential of staff to get better productivity and success for the organisation, something that is recognised by organisations such as the CBI.
Or an organisation can carry on appointing a self-perpetuating stereotyped minority and stagnate, because they are failing to tap the potential that is out there.