The National Association of Home Builders says its housing market index fell this month to the lowest level since last summer. The drop reflects fears that demand for new homes will be weak despite the extension of a federal tax credit for buyers.

The reading of 15 is the second-straight monthly decline and the lowest since June. It shows that builders are grim about their prospects even though Congress extended the deadline for a tax credit of up to $8,000 for first-time homebuyers and expanded it to include $6,500 for existing homeowners who move.

The index reflects a survey of 504 residential developers nationwide. Index readings below 50 indicate negative sentiment about the market.