19K is a landmark. It’s the highest inventory we had, and occurred during the last bust in July 1995, when layoffs and a recession caused thousands of workers to leave San Diego.
Since rising inventory increases DOM and decreases price, the inventory is a leading indicator of a price decline.
I guess the 19K number is a past glass ceiling, and surpassing it implies we are in another bust.
Once we pass 19K, the media headlines will announce this “Inventory at highest level since 1995 signals housing bust”, decreasing consumer confidence. And that will lead to even lower sales. The media reports caused by the 19K figure should depress seller motivation, the a factor which you noted.
I don’t recall if Pigginton mentioned the 19K number. It has been done by others, on RealtyTimes and the Voice of San Diego, and perhaps they can explain why they consider it a metric worth writing about