Jesse Eisinger and Justin Elliott:

American industry is more highly concentrated than at any time since the gilded age. Need a pharmacy? Americans have two main choices. A plane ticket? Four major airlines. They have four choices to buy cell phone service. Soon one company will sell more than a quarter of the quaffs of beer around the world.

Mergers peaked last year at $2 trillion in the U.S. The top 50 companies in a majority of American industries gained share between 1997 and 2012, and “competition may be decreasing in many economic sectors,” President Obama’s Council of Economic Advisers warned in April.

While the impact of this wave of mergers is much debated, prominent economists such as Lawrence Summers and Joseph Stiglitz suggest that it is one important reason why, even as corporate profits hit records, economic growth is slow, wages are stagnant, business formation is halting, and productivity is lagging. “Only the monopoly-power story can convincingly account” for high business profits and low corporate investment, Summers wrote earlier this year.