As jobs increasingly require college degrees, the Boston area’s highly educated workforce is a key reason that the region’s unemployment rate has fallen well below the national average, according to a study to be released Wednesday.

The report, by the Brookings Institution, a Washington think tank, studied job openings and educational levels in the nation’s 100 largest metropolitan areas and found a gap between the education that employers demand and the levels attained by workers.

The metro areas with the narrowest gaps had the lowest unemployment rates, while those with the widest gaps had the highest rates, according to the study.

In Boston, for instance, 48percent of job openings require a bachelor’s degree or higher, while 43 percent of the area’s residents have that level of education. The region’s unemployment rate was 5.3 percent in May, compared to an average of 7.9 percent across all metropolitan areas.

In McAllen, Texas, on the other hand, 32 percent of jobs required at least a bachelor’s degree, while 16 percent of residents had attained that ­level.­ In May, that area’s unemployment rate was 10.8 percent.

Across all the metropolitan areas, 43 percent of open jobs required at least a bachelor’s degree, but only 32 percent of adults had one.

“It’s really about supply keeping up with demand. We know that over the last few decades the demand for education has increased,” said the study’s author, Jonathan Rothwell, a senior research associate at Brookings.

“So the question is: Are workers keeping up with what companies are looking for? And the answer is that in many metropolitan areas, they are not.”

The divide between workers’ education and the marketplace’s demands has grown as companies rely more on technology and increasingly require workers to have degrees, Rothwell said. Conversely, in sectors that traditionally employed people with high school diplomas, such as manufacturing, technology is replacing workers.

Cities like Boston with large research universities tend to have more residents with college degrees because students tend to stay in the area after they graduate.

More than 60 percent of college graduates live in the state where they attended school 10 years after they finish, according to the study, and 45 percent of the founders of large technology companies start their businesses in the same state where they attended college.

Short-term unemployment is affected primarily by volatile factors such as housing prices, Rothwell said, whereas education gaps, which develop more slowly, have more of an impact on long-term unemployment.

Boston is a tough market for people without a college degree. Last year, there were only 2.2 openings for every unemployed worker with a high school diploma or less, according to the study, compared to 5.9 openings for every worker with a bachelor’s degree or higher.

Companies today are less flexible than they used to be, said Eileen Habelow of the staffing firm Randstad, based in Woburn. Fewer companies will consider relevant work experience in place of a college degree, in large part because there are so many people looking for work.

“They get thousands of resumes per opening for some positions,” she said.

The solution to the education gap, Rothwell said, lies in improving primary education to prepare students for college, increasing the connection between employers’ needs and community college classes, and providing incentives for companies to offer more training.

“You’ve got to pull as many levers as you can to try and encourage people to get education and get training,” Rothwell said.