How does Stoller explain why since the 1970’s there’s been massive turnover whether you look at the largest 10 companies, the largest 100, or the largest 1,000?

Turnover might be due to mergers, takeovers and periods of monopolization of different sectors of the economy, turnover doesn't measure the level of monopolization or duo-polization. Market share and relative capitalization per sector are the valid measures.

OK, which sectors were monopolies (or even duopolies) in the 1970’s that have survived to this day? Maybe oil? A few agricultural sectors?

If you actually look at the corporations that are consuming Americans’ income in 2025 vs. the equivalents in 1975, the idea that “monopolies” have controlled the economy for 50 years is self-evidently absurd.

If the number of providers that you yourself have direct access to is singular or limited to two or three? Yes that's a monopolistic environment. Consider that for most people in many more regions of the US than not will only be able to access the internet with ONE provider. They will only be able to get health care from one provider. They will only be able to get farm equipment from one provider and then not be able to fix said farm equipment. They will only be able to get seeds for food from one provider. And where 1 or 2 platforms are the only way for distribution in the digital space ("cough" app stores) or your logistical choices come down to 1 or 2 with prices fixed...again you may have comeptition on some level but at the macro level monopolistic effects are occuring because the distribution channel is what moves a market not necessarily sub vendors.

the fact that the incentives for shareholder interest has led to consolidation and then to again always end up in a market where there is less providers than more. Look the names may change But since derregulation of much of the M/A activity we have ended up in markets that have monopolistic effects.

So...semantically there may be "competition" in markets" but on the ground and in real life where it matters the effects and actual restrictions that monopoly brings is very much a fact. It's absurd to ignore actual in depth analysis that takes context of actual economics (from the regional facets to actual mechanics of trade) into account and not think that monopolization is not occurring and not have an overwhelming impact. It is very evident that you yourself have not looked to deep into this.

He's right. The very reason free markets don't exist is the same exact reason why communism doesn't work in practice. All markets collapse until there's a few dominant businesses (ie monopolies), just as how society naturally forms governing hierarchies. And this is easy to see how they're opposed. All you have to do is look at how there's only 4 types of governments based on how decision making power is distributed, and that democracy is actually closer to communism on that spectrum rather than dictatorships, and then see how monopolies behave quite like dictatorships.

That said, true dictatorships rarely work in practice but for different reasons as to why communism doesn't work. Which is why, when it comes to organizations, almost all are in fact oligarchies in practice, despite whatever they're called. This is known as the iron law of oligarchy. Notice the term: oligopoly? Go look at every industry and there's near always an oligopoly.