As the housing crunch continues, the city of Boston is considering a new tax on big real estate deals with the money earmarked for more housing. Barry Bluestone is professor emeritus at Northeastern University, and before that he was with the Boston Foundation. Bluestone is an expert on housing. He spoke with WGBH All Things Considered anchor Barbara Howard about the proposed tax. This transcript has been edited for clarity.

Barbara Howard: We're talking about a 6 percent tax on sales of over $2 million, both commercial and residential sales. Advocates project that this could possibly raise upwards of $350 million a year. What kind of a dent would that money put in the housing crisis?

Barry Bluestone: Well, if we could get $350 million from such a tax, we could certainly use that to subsidize more affordable housing.

Howard: Besides the 6 percent tax, the Boston City Council is also considering a "flipping tax" of up to 25 percent on properties that are sold more than once within a period of two years. Investors often snap up properties and develop them, to flip them for a profit. But could this proposed tax backfire? As in, would developers leave properties vacant for a while before selling them to avoid that 25 percent tax?

Bluestone: There are always unintended consequences when you do anything. I think the idea of a "flipping tax," perhaps not at 25 percent, is actually something that should be considered. We have a lot of housing that is being built purely on speculation, not really for people to live in. I keep telling people, we build a lot of luxury housing, but I'm not sure it's housing, because nobody lives there. They’re really bank vaults. Here's a way of capturing some of that revenue which could then be used to subsidize affordable housing.

Howard: The real estate transfer tax would have to be passed by the Boston City Council, then signed by Mayor Marty Walsh, and then it would still need approval from the state legislature. What do you see as the prospect of this clearing all those hurdles?

Bluestone: Not very good. We've been having trouble getting some of the more progressive legislation through the legislature. Politically, this is very difficult. We have transfer taxes in other cities, none of which are up to 6 percent. But I wouldn't do it at 6 percent. I would do it as a graduated tax, so that for the very highest end — like the $10 million properties, the $15 million, or the $100 million commercial properties — I could see that going up to 5 or 6 percent. But I would like to see a progressive tax that might take us from, let's say 1 percent, up to 6 percent, depending on the value of the building. And that would really hit the very highest end and raise some revenue there, but it would do it without some of the unintended consequences.

Howard: There are of course developers and others who are going to resist any kind of taxes like this.

Bluestone: And their argument is, if you put enough of this onto the developer, they're going to stop developing. Particularly when the market softens, when it slows down.

Howard: And what happens if the market softens and these taxes are in effect? Could that backfire?

Bluestone: It potentially could backfire in terms of less new development. We need to continue to build lots of new housing. Mayor Walsh has now upped his number to 63,000 proposed new units by 2030 to house what could be 100,000 more residents in Boston alone.

What we need to do is find a way of developing housing that's affordable to working families. We know how to build housing that's luxury housing for the rich. We even know how to build housing for very poor people, because we have a lot of federal and state subsidies. What we don't know how to do is build housing for families who are working families who have an income of, let's say twice the poverty line, maybe $50,000 to about $125,000.

And those are the people who are fleeing Boston, fleeing Somerville and Cambridge, just to find affordable housing.

Howard: And those families are the ones who often are serving the people in Boston and doing some of the medium-wage and minimum-wage jobs?

Bluestone: Yes, they are the service workers, but you even have teachers and firefighters who are having to move further and further out of the city.

One of the most stunning statistics in 15 years of housing report cards that we put out every year was that in 2017, the percentage increase in home prices in Lawrence was higher than the percentage increase in Newton or Brookline. And the reason behind that is the pressure on those housing markets — Lawrence, Lowell, Haverhill, other cities — has grown so much because people have had to flee the city to find lower-priced housing. And the demand in those presumably lower-housing cost cities has risen so fast that prices are now rising in those communities as well.

Read more: Greater Boston Housing Prices Still Rising

Howard: Making it harder to find housing there.

Bluestone: Exactly.

Howard: That's Barry Bluestone, professor emeritus at Northeastern University and an expert on housing. He was formerly with the Boston Foundation. He was talking with us about the proposal being considered by the Boston City Council to put a new tax on high-end real estate deals, with the money going towards more housing in Boston. This is WGBH’s All Things Considered.