Very informative article. The bottom line is that corporations have grown so large and have gobbled each other up to the point where there are less public companies today than in the past, and the biggest companies are practically monopolies:

The decline in listed companies has been so spectacular that the number is lower than it was in the early 1970s, when the real GDP in the US was just one third of what it is today.  America’s economy grows ever year, but the number of listed companies shrinks. On this trend, by 2070 we will only have one company per industry.

And some examples:

Two corporations control 90% of the beer Americans drink.

When it comes to high-speed internet access, almost all markets are local monopolies; over 75 percent of households have no choice with only one provider.

Four airlines completely dominate airline traffic, often enjoying local monopolies or duopolies in their regional hubs.

Five banks control about half of the nation’s banking assets.

Many states have health insurance markets where the top two insurers have 80-90% market share. For example, in Alabama one company has 84% market share and in Hawaii one has 65% market share.

Four players control the entire US beef market.

After two mergers this year, three companies will control 70 percent of the world’s pesticide market and 80 percent of the US corn-seed market

Employees are stuck at companies that pay them low wages because here aren’t enough other companies in the same industry left that can afford to pay higher wages and still compete.

Monopolies were always considered bad because without competition, monopolies can charge super high prices, but now we’re seeing that they are bad as well because they are keeping wages low and contributing to inequality as a result.

Source: Why American Workers Aren’t Getting A Raise: An Economic Detective Story | Jonathan Tepper