To comprehend the scope of corporate consolidation, imagine a day in the life of a typical American and ask: How long does it take for her to interact with a market that isn’t nearly monopolized? She wakes up to browse the internet, access to which is sold through a local monopoly. She stocks up on food at a superstore such as Walmart, which owns a quarter of the grocery market. If she gets indigestion, she might go to a pharmacy, likely owned by one of three companies controlling 99 percent of that market. If she’s stressed and wants to relax outside the shadow of an oligopoly, she’ll have to stay away from ebooks, music, and beer; two companies control more than half of all sales in each of these markets. There is no escape—literally. She can try boarding an airplane, but four corporations control 80 percent of the seats on domestic flights.

Politicians from both parties publicly worship the solemn dignity of entrepreneurship and small businesses. But by the numbers, America has become the land of the big and the home of the consolidated.

This is a problem. But it is not an accident. The bigness of business is a result of federal policy, which, in the past three decades, has deliberately made it easier for large companies to dominate their markets, provided that they keep prices down. After years of sluggish wage growth and low levels of entrepreneurship, some people are starting to worry that America’s biggest companies are growing at the expense of the economy, even if they offer consumers good deals.

In the late 19th century, when the U.S. was beginning to develop into an industrial powerhouse, it was America’s first small-business owners—farmers—who initially pushed the government to intervene against trusts. They protested discriminatory shipping rates along rail lines, which were dominated by a handful of railroad magnates.

Congress passed the Sherman Antitrust Act of 1890 to break up the trusts and protect competitive markets, but it took decades for the law to serve this purpose. (In fact, in the 1890s, the railroads used the act’s language against their own workers, arguing that a labor-union strike amounted to an illegal “conspiracy to restrict trade.”) Several Supreme Court decisions ultimately stiffened U.S. antitrust law. Perhaps the most important decision came in 1911, when the Court ruled that Standard Oil Company of New Jersey’s ownership of nearly 90 percent of U.S. oil production violated the law.

The early antitrust reformers warned that even beyond its effect on prices, economic power could buy influence in Congress. Monopolies don’t just dominate their own industries, Justice Louis Brandeis said in 1933; they monopolize political power as well, which allows them to protect their incumbency and stifle competition in myriad ways. The trust-busting ethos gathered momentum; President Roosevelt transformed the antitrust division of the Justice Department from a tiny office of just over a dozen lawyers to a muscular force of nearly 500.