Teachers play a vital role in society and the economy, but school systems are seeing a shortage in qualified teachers. That’s in part because teachers often can’t afford to live where they work, according to a new study.

Nearly a third of the country’s largest cities have cost-burdened teacher populations, where they pay more than 30 percent of their income on housing, according to Apartment List, a rental listing website. The problem is worse in major coastal cities: San Francisco, New York and Seattle round out the top three most unaffordable markets for teachers. Boston ranks as the fifth most unaffordable city for teachers, with educators having to spend 46 percent of their income on housing.

Those figures are for teachers with five years of experience. Teachers just starting out, and therefore making less on average than teachers with experience, have an even harder time finding affordable housing in major cities, according to the study. In fact, cost-burden increased as teachers gained experience in most cities.

Impact on teachers

Cities are dependent on teachers, but what happens when they can’t afford to live in the city where they teach? Some live elsewhere, and therefore spend more money and time on commuting.

Apartment List looked at the communities nearest major cities where teachers would not be cost-burdened. In San Francisco, Seattle and Washington, D.C., those affordable communities were at least 45 minutes away from the city during rush hour driving times. In Boston, the average travel time from work to the affordable communities is about 30 minutes, according to the study.

Increased travel time can have a negative impact on teachers and the schools where they are employed.

“Teachers priced out of urban markets sacrifice a significant amount of time each day commuting to the classroom, and may choose to teach in a different school district or leave the profession entirely,” the report reads. “School districts in expensive coastal cities risk losing both entry level and more experienced teachers because they can no longer afford to live where they teach.”

How to address

Of course, one idea is to pay teachers more money. Public school teachers in 2015 earned 17 percent less than other comparable workers, according to Apartment List. They made 2 percent less than other workers in 1994 and actually made 5.5 percent more in 1979.

Another possible solution would be build more affordable or “workforce” housing. Those proposals are not new to Boston, but it’s a solution which is much easier to say than do. Boston actually ranks seventh in the country for providing affordable housing in desirable areas. Even still, soaring housing prices in the area have effected all kinds of workers, including high-earning tech employees, leading to what some have called a “brain drain.” With home prices still creeping up, there is more work to be done on affordable housing in the area.