Admittedly, the United States contributes far fewer people to the global offline pool than do much larger countries, such as India and China, or even smaller, less developed countries, such as Nigeria. Still, it’s a striking reminder that problems of Internet access and adoption are by no means solved in this, the capital of tech innovation. It’s extra striking, given that the report was sponsored, in part, by Mark Zuckerberg’s Internet.org — you know, the starry-eyed “global partnership” dedicated to bringing the riches of the Web to the deprived foreign masses.

A great deal of research has been dedicated to America’s offline population already, of course. We know that roughly 20 percent of Americans don’t use the Internet — and per the Commerce Department, almost half don’t really want to.

But McKinsey suggests the gap is about more that mere interest. While the United States, like Russia and South Korea, has a large population of people who just don’t care to go online — a preference that, frequently, relates to age — there are serious issues of affordability and infrastructure, too. America’s disconnected tend to be literate, low-income women living in rural areas, where Internet access is either difficult or expensive to come by. In fact, America’s Internet divide can be seen primarily as a class divide: 80 percent of the country’s offline population falls below the poverty line, the highest proportion in any other country except Mexico.

Take a minute to think about that, dear Internet-enabled reader: In the country with the world’s highest GDP, the country that brought you Google, Keyboard Cat and the iPhone, more than 50 million people do not have access to the Internet — often, though not always, because they can’t afford a computer, smartphone or data plan. To whit, the Pew Research Center estimates that roughly 99 percent of U.S. adults in high-income households use the Internet; meanwhile, in low-income households, only 77 percent do.