The Los Angeles Business Journal’s index of largest local public companies closed down slightly for the week as the broader markets fell due to concerns that the U.S. Federal Reserve may scale back its bond-buying program.

The weighted LABJ Stock Index fell less than 1 percent to close at 145.31 for the week ended Feb. 22. Decliners outnumbered gainers 94 to 67, with nine companies unchanged.

Most of the biggest movers were influenced by fourth quarter earnings reports.

Among the biggest decliners was Torrance’s Motorcar Parts of America, which dropped 18 percent to $5.78 after a hedge fund investor criticized the company’s performance.

Westwood Wi-Fi hotspot provider Boingo Wireless Inc. dropped 15 percent to $6.77 as the technology company missed Wall Street expectations for net income in the fourth quarter.

Calabasas healthcare staffing firm On Assignment Inc. also dropped 15 percent to $20.91 as the company missed analyst projections for fourth quarter net income.

Among the biggest gainers was Pasadena nanotechnology firm Arrowhead Research Corp., which climbed 18 percent to $2.10. The company announced that its loss narrowed for the quarter ended Dec. 30.