Tl;dr, 10% of UK authors make 58% of the money. Worse, the top 5% earn 42.3% of the total money being paid.

Oh, and then there’s this Fun Factoid:

There is still a gender gap in earnings of professional authors, with women earning 80% of what their male counterparts earn. This is a larger gap than the population as a whole, where women earn 91.5% of what men earn.

Apparently this shrinks (to 97%) when the scope is changed from “professional authors”, defined as “those who dedicate more than 50% of their time to self-employed writing”, to “all writers”.  I’d be interested to know if anyone’s looked into the causes of that gap, particularly as it related to whether there are just straight-up more men than women who are able to be defined as “professional authors” (I wouldn’t be, under this metric, for example).