Because 71% of the workforce is preparing to quit.
To do what?
FTA: CWJob's research found that 14% of tech workers would look for a new role at a different company, with others planning to establish their own business (11%), go part-time (11%), change locations (11%) or become a contractor (10%). Eight percent are contemplating leaving tech altogether.
preparing seems to be the keyword here. This has no correlation to what will actually happen.
The UK, like the US has pronounced wage differences between regions, but unlike the US we're all in the same timezone. As a result you now get significantly better London wages being offered to northern workers, combined with the cluster that is IR35, brexit and increased demand for these skills from CoVid. Perfect storm of demand surges, supply contracts, wages go up.