Here is an in-depth study about the phenomenon in the European Union, but with data about the United States and Japan (and with interesting charts):  The Labour Income Share in the European Union

The evolution of the labour income share involves issues of equity, economic efficiency as well as macroeconomic stability as it has, for example, an impact on personal income distribution and social cohesion, the direction of the adjustment in wages and employment, and the composition of aggregate demand.

This chapter illustrates how the labour income share in the EU started to decline around the second half of the 1970s and fell towards levels that are below those that were attained in the 1960s. In addition, the chapter also shows that the share of the lowskilled workers in the total wage bill fell gradually while the share of the high-skilled workers rose steadily.

I didn't have time to read it all, but I want to highlight one thing: not only the share of labour in the GDP has been declining, but within the share of labour, inequalities are rising.

Secondly, there was also an important change in the composition of the wage bill, with the share of the low-skilled showing a marked decline and the share of the high-skilled workers displaying a steady rise.

We must not forget that the share of labour includes the wages of the top management. As Picketty and Saenz have shown, salaries contribute significantly to the top 1% income.

"Dieu se rit des hommes qui se plaignent des conséquences alors qu'ils en chérissent les causes" Jacques-Bénigne Bossuet