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This study suggests
Three-fifths of this gap is explained by the growth of inequality which widened the wedge between mean and median employee wages. A further third is due to the increase in non-wage labour costs, in particular the growth of employer pension contributions.
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The original chart you linked to just talks about "real average" so it's hard to know whether that's mean or median.
The link on productivity is odd, really it should compare median productivity to median wages. Is there "inequality of productivity" as well as "inequality of earnings", or are lower earners just getting paid a lower and lower share of what they produce?
It could be but that chart doesn't give you that information. Looking it up, labour's share of national income has recovered to pre-crisis levels over the last few years (figure 4) so I don't see the evidence that corporate profits are taking a bigger share of GDP.
https://www.ons.gov.uk/economy/economicoutputandproductivity/productivitymeasures/bulletins/labourcostsandlabourincomeuk/2022#labour-share-of-income