wrote in message

The market doesn't decide. The NHS is short of doctors but that hasn't
caused the number of students doing medicine to rise.

That's not a particularly good example. The number of places in .uk medical
schools is very much regulated by government. Many potential medical
students, who would probably be capable of qualifying, fail to gain a place.
However, the market does have an effect on the number of those who qualify,
but do not work in the NHS, either because they work in other fields or go
abroad. Against that, the NHS employs many doctors who have qualified
elsewhere in the world.

Peter