The Los Angeles Business Journal’s index of largest local public companies closed down slightly for the week as investors awaited action in Congress on a deficit reduction plan.

The weighted LABJ index fell 1 percent to close at 116.41 for the week ended Nov. 18. Decliners outpaced gainers 96 to 67, with 12 companies unchanged.

The largest decliner was Cereplast Inc., which fell 42 percent to $1.15. The El Segundo producer of environmentally friendly plastic resins for packaging, which earlier announced a dilutive stock offering, reported mixed third quarter results.

Arrowhead Research Corp. fell 26 percent to $5.53. The Pasadena nanomedicine company’s stock was adjusting to a 1-for-10 reverse split of common stock, which was trading for only 65 cents before the split.

Boingo Wireless Inc. was the week’s biggest gainer, gaining 14 percent to close at $8.98. The Los Angeles Wi-Fi hotspot provider announced an agreement with a South African company that will give Boingo customers access to an additional 600 hotspots there.

Beverly Hills concert promoter Live Nation Entertainment Inc. rose 12 percent to $9.18. Liberty Media Corp., a minority investor, announced plans to eliminate its tracking stock that included its Live Nation stake, and combine Liberty Starz and Liberty Capital stock into one asset-backed stock.