It can't be an 'endogenous' Marxian slow down in the real rate of accumulation--and the resultant explosion of financial speculation--that explains the stagnant character of even so called booms, this relative stagnation also explaining the runaway immiseration of the third world whose supply of immigrants is then considered an 'exogeneous' shock.
No free markets are fine, dynamic and just (something to do with Euler's theorem) unless messed with by exo shocks: govts, unions and immigrants.
Just like there is a tendency towards full employment unless there is a mass outbreak of a desire for leisure or rapid dysgenic trends in the relevant subpopulation. No reason not to venerate the market system.
As for arguments about mobility: This is movement over the life cycle from from one reification to another, right? That is, from one income quintile group (that arbitrary construct; based on what kind of theory do we cut the population like this?) to another, perhaps to the second income quintile group; maybe even in rare occurences to the third (probably counterbalanced by movements from the third to the second in some peoples' life trajectory).
Yet in the final analysis, no net movement out of wage labor has been demonstrated. So all this does not impact on the Marxian thesis. There is no net movement into the the bourgeoisie especially on a world scale. Quite the opposite, though the income share of the bourgeoisie, ever diminished in number, remains the same. Wealth is ever more concentrated.
Having thought Nathan was Max's svengali, I am surprised by Nathan's sharp comments. Let's see where this leads the syndicalist in relation to the social democrat!
Yours, Rakesh