An index that measures new multifamily housing recently reached its highest quarterly reading since the housing boom.

For the fourth consecutive quarter, the National Association of Home Builders’ Multifamily Production Index rose during the second quarter.

"Multifamily rental construction is trending upward, and it is definitely the brightest sector in the broader housing market," says NAHB Chief Economist David Crowe. "However, the entire housing market continues to be very fragile and subject to many external pressures, including an ongoing shortage of financing for new projects."

The Multifamily Production Index increased from 41.7 in the first quarter of the year to 44.4 in the second quarter — its highest quarterly reading since 2006. The index has continued to improve since reading a record low of 16 in the third quarter of 2008.

During the second quarter, developers reported seeing the biggest improvements in the production of low-rent units and market-rate-rent units.

"Even though multifamily is trending upward, production is still very low in a historic context and in the context of what we project is necessary to meet long-term demand," Crowe said.