Meanwhile, the rate of profit compares book profits (which are certainly not the only source of elite surplus-value-derived income) to the underlying capital stock. Those who dwell on this statistic are mainly trying to express their religious fealty to Marx's half-baked FROP theory. The implication of this view is that capitalism is impossible in the long run, because it snuffs out its own profitability. Does that sound realistic to you, Dick? It does not to me.
The Sweezy argument is that, because of the advantages of bigness, corporations prove to be very effective long-run maximizers of elite property incomes. Their effectiveness is such that there tends to be more money at the top than those at the top can easily re-invest. As a result the masters of the universe seek "artificial" (non-free-market) ways to boost their ability to make more money from last year's income. These artifices include military spending, financial speculation, and corporate marketing to stimulate demand for the products sold by the corporations in one's portfolios. As corporate capital proceeds, these items all tend to grow along with it. Sound a bit more explanatorily powerful, Dick? I think so!
The upshot of the latter view is that capitalism is irrational at its very core, as it requires immense amounts of social and ecological waste, all to prop up a ruling class that insists on always expanding the waste and irrationality, despite its immense and growing wealth and power. Capitalism does not and will not snuff itself out (at least not at the economic level). It can and must be replaced by democratic socialism.
It's all about realism and explanatory power. I think you'll find more of that in Baran and Sweezy than in all the FROP stuff put together. Let us know if you concur...