Still, speeds in the United States remain behind those in the world’s most connected countries, like South Korea, Japan and Switzerland. Equally importantly, American broadband, at an average price of $6.14 per Mbps, is more expensive than in most other developed nations.

This has little to do with the actual cost of moving bits. The price of transporting data wholesale across the Internet has fallen to about $1.57 per Mbps, down from $1,200 when Mr. Medin was helping start @Home. And high prices discourage Americans from opting for higher speeds. Though 10 Mbps broadband is available in 90 percent of homes around the country, and four out of five homes have access to 100 Mbps service, last year only 28 percent of homes that had access to broadband at a speed above 6 Mbps actually bought it.

What’s most worrying is that the handful of companies offering high-speed broadband to American consumers may have little incentive to expand their networks, increase their speeds and lower their prices.

According to the F.C.C.’s latest calculation, under one-third of American homes are in areas where at least two wireline companies offer broadband speeds of 10 Mbps or higher. Even including the spottier service offered by wireless providers, which tends to come with strict data caps limiting use, the share is less than half.

That means that in most American neighborhoods, consumers are stuck with a broadband monopoly. And monopolies don’t strive to offer the best, cheapest service. Rather, they use speed as a tool to discriminate by price — coaxing consumers who are willing to pay for high-speed broadband into more costly and profitable tiers.

Blair Levin, who headed the F.C.C.’s broadband initiative until three years ago and is now at the Aspen Institute, traces the roots of broadband’s limits to telephone companies’ decision, back in the 1990s, not to match cable’s costly investments in fiber, trusting that their DSL service would be an adequate competitor.

But DSL couldn’t follow cable past 3 Mbps. Verizon did eventually get on the ball — investing in its FiOS fiber network, which is expected to reach 17 million homes when it is completed. But that’s the exception.