In unused productive capacity; in Japan; in decade-by-decade growth rate declines; in jobless recoveries; etc.; etc. Read the book again.
> John Bellamy Foster's article seems to conflate the rate of profit and the
> rate of surplus value. I read Baran and Sweezy's Monopoly Capital some
years
> ago, but if I am not mistaken, its core argument seemed to rest on
> underconsumptionist assumptions.
Wrong. It's an overaccumulationist argument -- too much wealth at the top. Again, re-read the book. It's all right there. Quite simple, quite powerful. Such a shame so many bright people neglect to spend the ten hours it takes to work through Monopoly Capital. It's very dated in spots, but no other book explains so much of the contemporary world.