If the gap between technology rich and technology poor was primarily physical in the 1990s, the gap in this decade is increasingly skills-based.

To be “left behind” in the 21st century now means something completely different compared with what it meant at the end of the 20th. Then, Washington worried about getting enough telephones and personal computers into U.S. households. Although that challenge may seem like a distant memory, it has since been replaced by others.

Today, access to high-speed Internet — and the know-how to use it — have become regulators’ chief worry. They not only pose new problems for society but also, in subtle ways, change who needs the most help.

“It has more to do with knowledge and information literacy,” said Mark Warschauer, an education professor at the University of California at Irvine and author of the book “Technology and Social Inclusion: Rethinking the Digital Divide.”

Yes, cost is still a factor. As many as 10 million U.S. households without Internet access say they might be convinced to sign up for Internet service if they received a government subsidy, according to Federal Communications Commission estimates. But if that sounds like a lot, it pales in comparison to the two-thirds of non-Internet users in the United States who say they don’t intend to sign up for broadband — at any price.

A recent study by the Pew Research Center found that only 19 percent of the 51 million people without Internet access blame high prices, and only 7 percent cite the availability of broadband. Those who aren’t on the Internet today are saying they lack something else: the guidance that would make it an object of value to them.

Far more, 34 percent, told Pew that the Internet simply isn’t relevant to their lives. And 32 percent said it is too hard to use. In other words, adding more connectivity won’t close the digital divide if those who stand to benefit aren’t interested in what the Internet has to offer.

Coaching low-income Americans to look up information or apply for federal benefits online, or showing seniors how the Internet can help them stay in touch with family members, are difficult goals to measure. They don’t lend themselves to reports about numbers of homes connected or miles of cable laid. But the evidence suggests that policymakers already have reached the vast majority of households for which accessibility, or price, was the single biggest barrier to adoption.

Some aspects of this newer, skill-based digital divide promise to resolve themselves over time. Take seniors, for example, who account for one of the fastest-growing groups of social media users (despite their overall reputation as late-adopters, generally). As mobile apps and devices become more ubiquitous, younger generations are finding it easier to introduce the technology to their parents. And as the oldest Americans are gradually replaced by their children, the older-than-65 crowd will become filled with people who are more accustomed to using the Web.

“There’s no question that 15 years from now, it’s just going to be ubiquitous because the people of Gen X are then going to be in their 60s and 70s,” said Jody Holtzman, a senior vice president at AARP.

Still, addressing some aspects of the digital divide probably will require more active investments. The poor and the elderly tend to fare the worst, along with rural Americans and racial minorities. Households living on less than $25,000 a year, for example, are half as likely to use the Internet compared with those earning $100,000 or more. Although blacks and Hispanics have significantly increased their rates of Internet usage since 2005, they still lag behind other groups — and what’s worse, according to Pew, their progress has stalled.

For minorities and the poor, community centers and public libraries provide free access to broadband and online literacy programs that teach important tech skills. But these groups often complain that they need more funding for Internet connectivity, particularly in crowded urban settings and in hard-to-reach rural areas.

As many as 22 million rural Americans lack access to download speeds of 25 megabits per second, according to the FCC. One in 5 rural Americans lacks access to even slower speeds of 4 mbps.

Meanwhile, while only 8 percent of urban Americans lack access to basic broadband, the FCC has said, that figure surges to 63 percent among those living on Native American tribal lands.

Government programs and private initiatives have helped to close this gap considerably. The FCC said in August that it would award more than $9 billion to Internet providers such as AT&T, Frontier and Windstream over the next six years to help them extend their broadband infrastructure in rural areas. An FCC program known as Lifeline is expected to begin offering low-income Americans subsidies for high-speed Internet plans. The White House is funneling an extra $1 billion a year into connecting schools and libraries to the Web. And with varying success, city governments nationwide are pushing to build their own high-speed networks in places where commercial Internet service is nonexistent or subpar.

A slew of Washington agencies this year have pledged to make broadband more accessible. They include the Justice Department as well as the Department of Housing and Urban Development, which is considering a proposal to automatically wire new low-income housing with built-in data connections. Tech giant Google has offered to connect residents in such buildings to high-speed fiber optic service for free.

Other firms provide basic Internet access to low-income Americans at a discount. A Comcast program recently began offering some Florida seniors and community college students in Illinois and Colorado Internet access for $10 a month. And Facebook’s Internet.org initiative is exploring the use of satellites to beam wireless broadband down to less developed countries, an idea that could spread.

But all of these efforts to build more extensive high-speed networks still overlook what Pew, AARP and others have been discovering: that to get the last of the United States’ late adopters online will take more than infrastructure. It’ll require deep investment in digital education and painstaking one-on-one work that ultimately convinces offline Americans that the Internet is worth their time.

As the country closes that gap, still others will open as new technologies come along, displacing the Web as the next killer utility and the key to unlocking the nation’s economic future. That could be self-driving cars. It could be virtual reality. But how we answer today’s charge will directly determine how prepared we are for it.