The average price of commercial real estate across property types increased 2.5% in September from the previous month, according to a national index, but that change is likely an aberration in an otherwise downward trend, according to the index’s owner.

Transactions in September resulted in an index value of 173.92 on the Moody’s/REAL National All Property Type Aggregate Index, producing the slight upward bump in prices. Over the past 12 months, however, the index value has dropped 7.9% and is now 9.4% below a peak recorded in October 2007.

“Prices have not yet reached bottom and the index will resume a downward trend,” says Neal Elkin, president of Real Estate Analytics LLC (REAL). “The overall increase in the index masks double-digit declines in several sectors, which point to weaknesses in this asset class over time.”

Three of the four national property types saw modest price increases in the third quarter as measured by the index, according to a report published by Moody’s Investors Service. The exception was the national office market, which posted a 1% decline from the second quarter. Office prices in the top ten cities increased by 2.2%, down just 1% from the overall peak level. The Western office market underperformed the nation, with a decrease in prices of 5.5%, with the index standing 10.6% below its peak.

The Moody’s/REAL Commercial Property Indices are owned by Real Estate Analytics. Moody's publishes the indexes monthly using data from New York research firm Real Capital Analytics Inc. Engineered by the MIT Center for Real Estate, the indexes track repeat sales, or how much a sold property has changed in value since the last time it traded.

Market observers say that the combined effects of reduced transaction volume brought on by the credit crunch and a flight to quality in 2008 have masked the extent of falling asset values this year. That’s because sales-based indexes reflect the uncharacteristically high proportion of high-dollar, trophy assets among the properties changing hands in today’s market.