From the latest MLS news release: "Housing inventory in Houston first fell below a six-month supply in December 2011 and has remained below the five-month level for the past three months, dropping in October from 6.6 months a year earlier to 4.4 months. That is the lowest level observed locally since December 2001. For perspective, the national inventory of single-family homes is 5.9 months, according to the National Association of REALTORS® (NAR). A supply of less than six months is traditionally defined as a "seller's market," although buyers have been able to continue taking advantage of historically low mortgage interest rates."
You can get full details from the news release here.