WASHINGTON—The Housing Market Index (HMI) rose two points in November, according to the National Association of Home Builders (NAHB).

The HMI measures builders' confidence in current sales, subdivision traffic (numbers of prospective buyers looking at homes) and expectations for future sales over the next six months. In November, the index rose to 49, up two points from the revised 47 index reading recorded in early October.

When combined with housing finance and other real estate related sectors, housing's share of the economy rises to about 20 percent of the nation's Gross Domestic Product.

The HMI is derived from a monthly survey of builders that NAHB has been conducting for nearly two decades. Home builders are asked to rate current sales of single-family homes and sales expectations for the next six months as good, fair or poor. They are also asked to rate traffic of prospective buyers as either high to very high, average or low to very low.

In November, traffic of prospective buyers increased from 33 to 39, and expectations for sales over the next six months increased by two points from 55 to 57. Current single-family sales were unchanged at 52.