WASHINGTON (TIP): Bill Gates is something of a model for education skeptics. Gates — like Steve Jobs, Mark Zuckerberg and Oprah Winfrey — dropped out of college. If they didn’t need a college degree, the skeptics suggest, maybe you don’t need one, either.

Gates has just published a blog post with something of a reply: Yes, you do need one.

“Although I dropped out of college and got lucky pursuing a career in software, getting a degree is a much surer path to success,” he writes.

“College graduates are more likely to find a rewarding job, earn higher income, and even, evidence shows, live healthier lives than if they didn’t have degrees. They also bring training and skills into America’s workforce, helping our economy grow and stay competitive.”

He adds, “It’s just too bad that we’re not producing more of them.”

The post is tied to an interview Gates has done with Cheryl Hyman, the chancellor of the City Colleges of Chicago, the city’s network of community colleges. During her five-year tenure, the system has started to raise its abysmally low graduation rate. One of her main pushes has been simplifying the course-selection process, so students know what courses they need to take and can enroll in them. The complexity of that process at many colleges is a bigger problem than many people realize.

“The problem isn’t that not enough people are going to college,” Gates writes. “The problem is that not enough people are finishing.” About one-fifth of the working-age population, he notes, have attended some college without earning a degree.

The attention that Gates and his foundation are putting on college completion is part of a broader push on the subject. The Obama administration has also started emphasizing college completion, as have some governors and mayors, both Republican and Democratic.

It’s still not clear exactly what works best in reducing dropout rates, but it is clear that doing so matters. As I wrote recently, two large recent studies suggest that college graduation itself matters. (And other studies have come to similar conclusions.) Not only do students learn from the courses they take, but they also learn the valuable skill of seeing something through to the end —of figuring out how to finish what they started and of gaining the confidence that comes with that success.

The broader economic weakness over the past 15 years— which has affected college graduates, too — has created a fair amount of cynicism about college. People worry, somewhat understandably, that the economy is a zero-sum game in which producing more college graduates will simply force those graduates to fight over a fixed number of good jobs. But the evidence points strongly in the other direction.

Education, as David Autor, the MIT economist, notes, is not a game of musical chairs. More educated societies generally become richer, healthier and better functioning over time. Take the United States, which led the way in making high school universal in the early 20th century. Or South Korea, which has rapidly expanded its number of college graduates in recent decades.

“It’s hard to find examples of countries that have not ultimately benefited from sustained investments in modern education,” Autor said. “The evidence favors the idea that human capital investments pay off over the medium and long term.”

I’ve pointed out before that even education skeptics aren’t skeptical about the value of education — and college — for their own children. One of the world’s most famous college dropouts isn’t skeptical about it, either.