With Maine’s largest and most diverse population and an outsized share of the state’s new jobs, Portland is a vital city both culturally and economically. But without more and more-affordable housing, the city’s prosperity will stall, along with the chances of success for low- and middle-income residents.

If people at a range of income levels don’t have the means to live here, businesses in Portland and the surrounding area will find it harder to attract and retain employees; workers will struggle with long, costly commutes from less-expensive parts of Maine, and the city will lose residents who pay taxes and contribute to the community.

Portland’s elected officials, affordable-housing providers and municipal planners have already recognized that this problem is too big for the market to address on its own. Instead, an innovative approach including both regulations and incentives is critical to the prospects of success of both the city’s residents and the city itself.

There’s not enough housing in Portland, and what’s there is too expensive. The vacancy rate in the city is roughly zero, and an average hourly wage of $19.46 – far above the hourly mean of $11.40 for Portland-area renter households – is needed to pay the local fair market rent of about $1,000 a month for a two-bedroom apartment.

Portland needs both affordable and market-rate units, to help take the pressure off other available housing and to ease the trend toward escalating monthly rental costs. If the Planning Board allows Bayside’s “midtown” retail and residential project to move ahead, it will help – though not to the extent envisioned before a lawsuit compelled the developers to scale back their plans.

The Planning Board is also reviewing the residential zoning for most of the Portland peninsula, with an eye toward encouraging the kind of multi-family housing that fits city residents’ needs but is actually illegal to build today.

Among other things, that means lowering minimum lot sizes, relaxing limits on the number of apartments in each building and cutting the number of parking spaces required per unit. The parking reduction, especially, could appeal to buyers (like the 77 percent of peninsula dwellers who are either carless or own just one vehicle) and developers (whose construction costs could be slashed by as much as a quarter if they didn’t need to include so much room for parking).

The zoning review is being undertaken at the request of the City Council’s Housing and Community Development Committee, which commissioned a workforce housing study that offers more information and suggests other policy options.

A common approach that could work here – inclusionary zoning – requires that “a certain percentage of units in a new development be set aside as affordable, with or without an increase in density.” In a recent memo to the City Council panel, Portland Planning Director Jeff Levine suggested that the city could tailor inclusionary zoning toward housing for a specific population that’s not served by today’s housing market, such as families making 80 percent to 120 percent of the area’s median household income (or about $60,000 to $89,000 a year in 2014).

The housing shortage also has costs for the community as a whole, such as food assistance to families who spend half their income on rent, or special help in school for kids who have trouble studying at home because their family is crowded into a small apartment with another family. So it’s in everyone’s best interest to make sure that nobody is shut out of the opportunities afforded by life in Portland because they can’t afford a good place to live.