SELLERS’ MARKET: Supply of homes for sale hits record low, and prices suddenly jump.

Sales of existing homes rose a steeper-than-expected 3.5% in December compared with January, according to the National Association of Realtors.

Demand is surging because mortgage rates are about a full percentage point lower than they were a year ago, and the largest generation, millennials, are aging into their homebuying years.

That demand has pushed the supply of homes for sale down 8.5% annually to the lowest level since the Realtors began tracking inventory in 1982.

At the current sales pace, the total supply would sell out in just three months. A six months’ supply is considered a balanced market.

I wondered what was up. A few weeks ago we started getting an attention-grabbing number of unsolicited letters from real estate agents we’d never heard of, more than one trying to entice us with mysterious-sounding “out of town buyers.”