Hart Capital Management Inc.'s Inland Northwest Composite, which gauges the aggregate market value of 15 publicly traded companies in the region, fell by $2.3 billion, or 19 percent, in the third quarter, as weighty market forces reversed earlier gains.

The Spokane-based investment firm reported earlier this month that as of Sept. 30, the composite stood at $9.5 billion, down from $11.8 billion at the end of the second quarter. That figure, in turn, was down steeply from a record high of $13.6 billion at the end of the first quarter.

The third-quarter drop brings year-to-date losses to $3.7 billion, or 28 percent, Hart Capital's report says. However, the total equity market value of the companies listed in the composite at the end of the third quarter remained $4.5 billion higher than a three-year low of $5 billion in March 2009.

During the latest quarter, 14 of the 15 companies in the composite declined in value, with the only one in positive territory being Sandpoint-based Intermountain Community Bancorp., showing a $400,000 increase in market capitalization. Market capitalization is share price times the number of outstanding shares.

Itron Inc., Hecla Mining Co., and Coeur d'Alene Mines Corp. showed the greatest decreases in quarter-to-quarter market value. Itron's value was down $754.6 million; Hecla Mining fell $646 million; and Coeur D'Alene Mines saw a $250.6 million dip.

Year to date, however, two companies held onto overall positive numbers: Avista Corp., of Spokane; and WTB Financial Corp, the Spokane-based parent of Washington Trust Bank. Avista had a $108.7 million increase in market capitalization since Dec. 31, while WTB Financial saw a $12.6 million rise.

In addition to the composite, Hart Capital operates an Inland Northwest Index, which tracks the same 15 companies in an index methodology similar to that of the Standard & Poor's Index. The index declined 18 percent in quarter-to-quarter comparisons, while the S&P 500 Index decreased 14 percent.

The best performers in the index over the three-month period were Intermountain Community Bancorp, up 4.2 percent; Clearwater Paper Corp., down 0.5 percent; and WTB Financial, down 3.5 percent. The worst-performing stock in the index was Itron, which fell 38.7 percent.

The 15 companies included in both the composite and the index are Avista, Ambassadors Group Inc., Clearwater Paper Corp., Coeur d'Alene Mines, Coldwater Creek, Hecla, Idaho Independent Bank, Intermountain Community Bancorp., Itron, Key Tronic Corp., WTB Financial, Northwest Bancorp., Potlatch Corp., Red Lion Hotels Corp., and Sterling Financial.