despite improved "human capital" formation in the working class as a whole and blacks in particular (higher high school completion rates, more post secondary education) * real wages* have remained stagnant or fallen, instead of risen as per marginal productivity theory.
An explanation of the wage structure seems to depend crucially on how the question is posed. The wage strucutre is not explained tout court any more than an eclipse is. Of the latter we ask how long it lasted ,or why it was partial, or why it was not visible from a certain place. My suspicion is that much apologetics in bourgeois economics are exactly in the few aspects of the wage structure, let alone the production process as a whole, it decides to explain. But of course this argument would have to be developed. Suffice to say, the kinds of causes you suggest may be adequate to explain a wage premium for skill (though as with all S&D accounts one is always left with the sense that the shifts themselves have not been explained) but not the declining condition of the working class a whole (the majority of which is only high school educated, though the real wages of male college graduates have also fallen for a decade), including in terms of the intensification of the work process, the increase in involuntary turn over, the debt incurred to acquire certain skills, etc.
Best, Rakesh
ps I have written more comments on the analysis which you submitted but I will think them over more before sending them.