@BarbaraofSeville The figures are from HMRC's income statistics, they include all declared income.
The situation with dividends would distort the figures a bit though.
Take a freelancer with a notional income of £100k (and no IR35 complications).
He draws £8,632 as salary.
The company pays £17,359 tax.
He draws £74,009 as dividends.
His taxable earnings on the the £100k he's earned are recorded as £82,641. He then pays £13,270 dividend tax, leaving a total take-home pay of £69,370 from his £100,000. Total tax paid between him and the company is £30,629. No NI to pay and the 'director' gets an NI credit as a low-paid employee.
If he received his earnings as a normal PAYE earner his employer could pay him £88,912 (the extra £11,078 goes to HMRC for employer's NI) and he'd have £60,103 take home pay - £9,267 less than using the Dividend/Salary split.
So under the first scenario his income is recorded in the stats as £82,641 but he comes out with £69,370. Under the second scenario his income is recorded as £88,912 but he comes out with £60,103.