Should German workers be paid more? Or, Do we have an omitted variable bias?

A recurrent problem in regression analysis is the omitted variable bias: if you estimate a regression and you do not include on the right side a variable that belongs to the model and is correlated with some included variables, the OLS estimates will be biased. The gist of this post is whether we have something of an analogous problem in addressing the current macroeconomic problems in the €-area, namely by not considering the possible influence of income distribution.