Research like this is really very silly.
Until the invention of the “Charge Card” in 1950 - created because some American guy was embarrassed his wife had to pay for a meal - everybody paid by cash or cheque.
Just 75 years ago, compared to the history of cash use, which goes back more than 2500 years.
Everybody was paid in cash in those days. Employers weren’t trying to avoid tax by doing so; there was no viable - or legal - alternative.
So let’s cut out this rubbish about “ the informal economy”.
This phrase is as valid as the word “cashless”.
Both are inventions of those who seek to push cash out by demonising its use.
Cash continues to be part of the UK economy - and every other economy on the planet.
Cash is FOREVER.
Source: lboro.ac.uk/media-centre/press-releases/2024/november/informal-economy-conversation