New research shows that large corporate landlords are responsible for nearly half of all evictions in Boston — and there could be an "eviction tsunami” if they don't agree to work with tenants when possible, advocates say.

“We asked, who is responsible for lots of evictions?" said Tim Reardon of the Metropolitan Area Planning Council, which partnered with the Boston Area Research Initiative on the new study. "If we can name them, then we can target interventions and outreach."

Reardon and his colleagues found that landlords who owned more than 100 units in Boston were responsible for 45% of all evictions in 2015 and 2016, even though they represented less than 0.5% of landlords in the market.

Their report, published Monday, identifies ten large corporate landlords who have yet to sign an “eviction diversion pledge,” promising to abide by the current federal moratorium, proactively engage with residents to create payment plans, promote rent adjustments for subsidized housing and conduct mediation in case eviction cases are filed.

“Now city councilors, the mayor or neighborhood development advocacy organizations can pick up the phone and actually call 10 specific landlords and say, we need you to sign this pledge. We need you to get on board," Reardon added.

Though small and medium-sized landlords make up almost 90% of all landlords and 44% of all rental units across the city, the report shows that they only make up 27% of all evictions.

“Our research also found that only 10% of evictions happen in buildings that are owner-occupied,” the researchers wrote, “further suggesting that small landlords who have a personal relationship with their tenants may be more willing to work with them to avoid eviction.”

Alexander Sturke, a spokesperson from the city’s Department of Neighborhood Development, said that the city has been calling landlords since October asking them to sign onto the pledge.

“One of the things that's difficult about those specific ten landlords is that it's not clear that they, five years on, are still the biggest offenders,” Sturke told GBH News. “So we will definitely call them, but because the data is so old, it's really hard to comment on what their current standing is.”

The city has worked with both BARI and MAPC to find more data on the biggest eviction offenders, Sturke said, but housing court data is difficult to attain.

“The housing court is notoriously difficult to get information out of," he said. "They're not forthcoming. We literally had to send people to physically go through physical files. There's no automated data system. There's no data dump that we could have gotten.”

The most recent data researchers and the city could access was from 2015 and 2015, Sturke said.

“Next year we'll have 2016 – 2017 data,” he said. “We're always like two or three years behind.”

Forrest Hangen, a researcher at BARI, sais this is a “first step” for city officials to begin to examine pandemic-related evictions, which may have different causes but are likely affected by pre-existing issues within the city.

“The data is still sort of opening up, and it’s still very much a difficult thing,” Hangen told GBH News. “We’re using the data to look at historical patterns of eviction, and there’s an assumption that the same and similar patterns are what's being enacted now.”

Reardon says regardless of the age of the data, it’s still important that big companies on the list, which operate a total of 4,000 rental units, are pledging to work with tenants to avoid large-scale evictions across the city.

“We can't say that those ten landlords who haven't signed are going to be responsible for a lot of evictions, but we know that they have been in the past,” Reardon said. “So it's worth calling them.”

The eight companies that have signed the pledge, according to the report, conducted an average of 75 evictions per year during the study period. Those who have not signed the pledge were associated with approximately 25 evictions per year during pre-pandemic times, “making them worthy of scrutiny and further encouragement to sign the pledge,” the report reads.

Eviction filings for non-payment in Massachusetts are consistently breaking 2020 records on a weekly basis, with 4,200 cases filed in housing court since the Massachusetts eviction moratorium expired in October, according to trial court data compiled by BARI and MAPC.

Last week, lawmakers in Washington, D.C., passed a COVID-19 relief act that extended a federal eviction moratorium from the Centers for Disease Control and Prevention, which took effect in Massachusetts after a state eviction moratorium expired. The federal order does not prevent landlords from filing eviction proceedings or verbally threatening eviction, and it doesn't stop tenants from having to pay rent, according to the Massachusetts Housing Court.

Because it doesn’t prevent landlords from moving forward with the written process of evictions, Reardon said the order doesn’t give tenants enough time to ensure that they won’t be evicted at the end of January.

“There's no way that a landlord could file and get an order to evict in the space that we have between the end of the state moratorium and even the new end of the [federal] moratorium,” he said. “The CDC process doesn't do very much, and nothing is preventing those informal evictions of people getting a notice to quit and then just saying, I'm not going to court, I'm not doing any of that — I’ll just move, cut my losses and then go.”

Reardon says this leads to situations where tenants are forced to choose between homelessness or doubling up with another group or family in a residence, “both of which are big risk factors for COVID-19, so it just kind of contributes to the spread of the pandemic.”