Boston is well on its way to exceeding Mayor Martin Walsh’s stated goal for the creation of new housing units set back in 2014, according to the city’s Department of Neighborhood Development (DND), which released figures this week showing that the city has already added more than 10,000 new units in the last two years. Add in housing starts currently under review or in construction and the estimated number jumps to 39,120 — or enough housing for 67,600 new residents.

It’s a “first wave” milestone that Sheila Dillon, who serves as Walsh’s housing chief as the director of DND, says is starting to have the desired effect of slowing, if not reversing, rental hike rates. While most of the housing units built in the last two years are in more affluent downtown or inner neighborhoods – like South Boston – Dillon says that many of the pipeline projects are in outer neighborhoods.

“We are now seeing many more developers interested in the outer neighborhoods and we believe adding new units there – as well as downtown – is what will alleviate pressure on the neighborhoods,” said Dillon. “The supply is doing what we want it to do.”

In a statement noting the 10,000-unit milestone, Walsh said that “Boston is growing faster than at any time in the last 50 years, and we need to make sure that anyone who wants to help make our city better can afford to live here. In today’s strong housing market, that means we have to create housing at all levels – from luxury units to housing for seniors and formerly homeless people. I am so pleased that we have reached this milestone, and we are not going to rest until we have reached our goals.”

Considered somewhat ambitious when it was released in October 2014, the administration’s call for 53,000 new units by 2030 now seems likely to easily reach the target perhaps years before the fourth decade of the millennium arrives. Whether that figure will be anywhere near what the city actually needs to house its burgeoning population remains an open question.

Dillon acknowledged this week that DND and the Boston Redevelopment Authority (BRA) are reviewing population growth projections with an eye toward adjusting the number upward. In 2014, the city thought that Boston’s population – now thought to be about 667,000 – would likely surpass 709,000 by 2030. “We may need to increase that, but the jury’s still out,” she said.

Also still unclear is whether the city’s guiding housing principle is correct on its premise – namely, that building more units will both ease demand for units and discourage displacement of existing residents.

Data show that rents have stabilized or even fallen slightly in Central Boston, which has seen 3,030 new units come on line since 2014. As people upgrade into the sparkling new condos or apartments, the city believes that helps folks find a more affordable living space in the vacated older buildings.

In South Boston, city housing officials say that supply has not yet caught up with demand, even though the neighborhood’s housing stock has seen more than 2,500 new units come on line in the last two years. Rents are up six percent in that time frame. Dillon notes that Southie, including the Seaport section, has added “enough floor space to accommodate 8,000 new workers.”

The pace in Dorchester and Mattapan has been but a whisper of the downtown boom. Dorchester has added 327 units and Mattapan just 201. But those numbers reflect completed units and, as regular readers of the Reporter know well, there are multiple large-scale housing starts already in the ground or in the mid-to-late-planning stages, particularly in Dorchester.

Projects like DotBlock, the Treadmark building at Ashmont, the South Bay expansion, Hub 25 at JFK-UMass, the Indigo Block in Uphams Corner, and Cote Ford in Mattapan are not factored into the 10,000 count. Neither are the 1,000 dorm beds on the UMass Boston campus, which will be occupied in 2018.

The growth rates in Dorchester and Mattapan – now at just two and three percent, respectively – are sure to grow significantly over the next 24 months. In fact, 69 percent of the permit applications in 2016 have been in what the city calls “the outer neighborhoods,” with 31 percent in the downtown core.