According to a release from New York City-based REAL, the index has now declined 19.1% year-over-year and is off 21% from its October 2007 peak of 191.87. The January index of 151.58 followed the December '08 index of 160.46, and is roughly equal to the April '05 level of 151.29. The index has not fallen below 160 since July of '05.

"While it is unsettling to see the sharp deterioration of commercial real estate values, the CPPI continues to perform as an accurate and timely benchmark for the asset class," says Neal Elkin, president of REAL, in a release. He adds that the January drop-off reveals that "declines are accelerating and permeating all regions and property types."

REAL began compiling the monthly index, which is derived from Real Capital Analytics transaction data, in December 2000. That month's index of 100 has served as the baseline for monthly increases or decreases. The index rose steadily until October '07 and began declining each month thereafter except for February and September '08.