The value of commercial properties owned by institutional investors rose 4.4 percent in the third quarter, its first increase in more than a year, according to an index managed by the Massachusetts Institute of Technology Center for Real Estate.

The index is based on the value of property transactions in the NCREIF index, which is managed by the National Council of Real Estate Investment Fiduciaries. It also uses appraisal information for roughly 6,000 properties acquired on behalf of pension funds.

The pricing index is still 36.5 percent below its peak, reached in mid-2007 before credit markets went into turmoil. But David Geltner, director of research at MIT’s real estate center, said the recent results are “reflecting the first increase in market sentiment” since the peak.

MIT’s index also found a distinct narrowing in the gap between what sellers are asking and what prospective buyers are offering for properties. Prices that buyers were willing to pay in the third quarter rose 12 percent, after declining for eight consecutive quarters, while the prices owners were willing to accept dropped 2.5 percent, and were 30 percent below the peak reached in mid-2007.

The index further found that sales volume increased during the third quarter, its second consecutive quarterly jump.

“One quarter does not a trend make, and we are still well below normal trading volume,” Geltner said. “Nevertheless, this is the strongest sign of a bottom that we’ve had in two years.”