How has the return on equities shifted in the risk-return plane?

We look at the change over time in the pair formed by the average excess return on equities and the variability in the return on equities in OECD countries. Companies in OECD countries have been characterised by: The skewing of income distribution in their favour; Increasing debt leverage; Concentration and dominant positions. We therefore expect the average return on equities to have risen more than the increase in the variability of return s (risk) would suggest , probably as a result of low wage growth and concentration. On the contrary, however, both the expected return and the variability of return s on equities have declined in the recent period.