Just 910,000 homes were on the market nationwide in December, marking the first time the number of available homes dropped below 1 million since at least 1999, when the National Association of Realtors started keeping track, the group said Thursday. That’s after an 18% drop in inventory from November. The chart below shows how the stock of available homes for sale has shrunk steadily since peaking in 2007. The decline in inventory contributed to a 4.6% dip in sales in December, the first time in four months that sales have fallen. The supply of homes would last just 1.8 months at the rate they’re currently selling. That’s also a record low, a major reason home prices have been soaring. Current supply represents less than a third of what’s needed for price increases to be at the moderate level, about six months, according to NAR.  Housing inventory usually dips during the winter, but not this low. Data from real estate company Zillow, also released Thursday, showed similar numbers.  “Home shoppers picked the shelves clean this December,” said Jeff Tucker, senior economist at Zillow, in a commentary. “Neither high prices nor slim inventories have deterred buyers so far.”Have a question, comment, or story to share? You can reach Diccon at dhyatt@thebalance.com.