The Los Angeles Business Journal’s index of largest local public companies gained more than 3 percent for the week ended Jan. 14, as the markets reacted to positive economic and earnings reports.

The weighted LABJ index rose 3.3 percent to 123.65, with gainers outpacing decliners 102 to 69.

Among the biggest gainers was downtown Los Angeles office landlord MPG Office Trust Inc., which jumped 26 percent to $5.25 on analysts’ optimism about the sector.

RadNet Inc. gained 22.5 percent to $3.70. The Los Angeles medical diagnostic imaging center operator completed an acquisition of a company that provides remote interpretation of X-rays and other exams, opening up a new business line for company.

Pasadena-based Jacobs Engineering Group Inc. gained 11.7 percent to $51.02 after an analyst’s upgrade and the announcement of new contracts.

Los Angeles homebuilder KB Home continued to get a boost from a positive earnings report the previous week and increased optimism about the sector. Share rose 9.6 percent to $15.71.

Among the largest decliners was China Mining Group Inc., which fell 11.3 percent to $5.90. The City of Industry operator of coal mines in the People’s Republic of China announced the closing of a 3.7 million-share private placement, with gross proceeds of $15 million.

Torrance coffee roaster and distributor Farmer Bros. Co. fell 10.9 percent to $15.59, in part on concerns about bad weather hurting crops in key coffee-producing regions.