As the Legislature considers ways to kickstart housing development, a new report concludes that restrictive zoning bylaws, applied with political considerations, contribute to a lack of multifamily units in Massachusetts.

The report, released Tuesday and compiled by researcher Amy Dain on behalf of organizations that have been clamoring for housing production legislation, found that many of the 100 communities around Boston — excluding the city itself — apply restrictions that prevent sufficient construction of homes that can fit multiple tenants.

The 123-page report reached four main conclusions:

that municipalities sharply restrict housing density either by written policy or practice, that zoning approval processes have become more "ad hoc" and "discretionary," that much of the new housing development has relied on mixed-use projects, and that communities continue to allow greater development on their edges rather than in historic centers.

"No municipality out of 100 is allowing, right now, as much multifamily housing to be built as the market demands," Dain said at a Tuesday forum about her research.

Advocates, including many of the groups that sponsored Dain's research, have been calling for years for state leaders to revamp how zoning processes work. They argue that a high barrier on new development has prompted a dramatic slowdown in production of new housing, putting pressure on the market and inflating prices.

Dain's new report focused specifically on the role of multifamily housing and the challenges to build new units in that category, a topic she first examined in a 2006 study. While progress has been made in recent years, Dain said that municipalities continue to "over-restrict" development.

Over a two-year period from 2015 to 2017, only 14% of multifamily units in the greater Boston communities Dain studied were permitted "by right." The vast majority of units required active discretionary choices by the host municipalities to be constructed, with about 57% under special permits and 22% under the state's Chapter 40B affordable housing program.

In an introduction to Dain's report, the groups that sponsored the work pointed out that the state has added 245,000 new jobs since 2010 but only 71,600 new units of housing.

"Massachusetts is the fastest-growing state in the Northeast, and yet our housing production has not kept up," Andre Leroux, executive director of the Massachusetts Smart Growth Alliance, said at the forum.

Moving forward, Dain said, communities should update their zoning policies to make multifamily construction easier to launch and should commit to increasing density, including by building units in historic centers and easing height restrictions.

Her report comes as the Joint Committee on Housing weighs a range of housing production bills, including one that Gov. Charlie Baker has made a key focus of his administration. The Baker legislation would reduce the threshold needed for zoning changes at the local level from a two-thirds majority to a simple majority, something that several speakers at Tuesday's forum explicitly supported.

"During my research, I kept hearing stories about projects that looked good and had majority support in the municipality but couldn't reach the two-thirds threshold to be passed," Dain said.

Several speakers stressed that Baker's bill, while valuable, would only be a "first step" ahead of additional action to prompt greater development, better access to affordable housing, and ways to protect tenants from rapidly increasing rents or evictions.

And for some, the latest report showcased how long it has taken to find a solution.

"We do all these studies ... and all it does is get worse," said Jeff Rhuda, business development manager at Symes Associates. "Something has to be done. Something works. Nothing doesn't."