What does this map represent?

Here is a map of the UK. As you can see different regions are shaded in different colours. (No data from the grey areas, I don't know why.) I've hidden the key, but can you guess what the map represents?
What does this map represent?
The percentage of people who marry a first cousin
The average price of a pint beer down the pub
The number of adults who've had a dental check up since childhood
The average number of stabbings per month
A man's income before girls will date him
A woke measurement of "inclusively".
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Updates
9 mo
It's the price of a pint in a pub, for example £5.59 in London, £4.87 Scotland, £4.74 Wales, and £5.21 South East England cheapest is NE at £4.56
What does this map represent?
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