The Los Angeles Business Journal’s index of local public companies rose this week, as a mending European debt crisis and a last-minute extension of a payroll tax cut buoyed the U.S. stock market.

The weighted LABJ Stock Index closed up 5.5 percent to 120.6 for the week ended Dec. 23. There were 121 companies that gained in stock price during the week, while 45 declined and seven were unchanged.

The biggest gainers included National Technical Systems, a defense and aerospace contractor that reported strong revenue gains on Dec. 15. For the week, the company’s stock rose $1.03 or 20 percent to close Friday at $6.18.

Korn-Ferry International, the executive search firm in Los Angeles, gained 13 percent to end the week at $17.43 after the Labor Department reported that unemployment claims fell to their lowest level since 2008. The same news helped On Assignment, a professional staffing firm in Calabasas. It gained 12 percent to end the week at $11.30.

Among the losers was toy maker Jakks Pacific in Malibu. It lost 19 percent to end the week at $13.99 after it issued a profit warning for the crucial fourth quarter. The company lowered its revenue guidance to $660 million, down from $770 million.