Redfin — as is quite often the case — has another interesting post on their corporate blog about real estate data.

Their numbers this month are about the continuing decline in inventory — down 18 percent compared to last year at this time. Everything I’m hearing from brokers and agents is that spring has come early, with more buyers out in the market. If inventories continue to be this low, it could put quite a squeeze on prices. Presumably that’s just what underwater sellers want, though it could make for quite a volatile market this year.

But it’s not so much Redfin’s overall numbers that caught my eye. It’s their breakdown which is really interesting. According to their data, the decline in inventory is being driven not by a drop in conventional sellers — that’s actually up 2 percent overall across their markets — but by a huge drop in distressed properties for sale, that is, shorts and REO.

It’s tough to say whether one single trend could be driving this change, since the proportion of distressed sales varies so much from market to market. In places like Arizona and Nevada, distressed sales have been a majority of the inventory for most of the past few years. Some market watchers are even worried about a new bubble in these “sand states,” so intense has investor interest been, and so rapid the price increases over the last six months or so.

But here in Boston, distressed properties have been a far small proportion of the overall market, and the investor feeding frenzy has been far more muted. Yet we’re seeing the same huge drops in short and REO inventory, according to Redfin’s data.

Could it be that bank’s distressed pipelines are finally running dry? Or are they simply so clogged with red tape (and new loan modification programs) that they’re slowed to a trickle? Or have the big banks deliberately pulled back in the hopes of slowing down sales and possibly taking a profit in a rising market?