The Los Angeles Business Journal’s index of largest local public companies gained for the week, as the markets reacted to unexpectedly good earnings reports from some big national companies.

The weighted LABJ Stock Index closed up 1.69 percent to 126.45 for the week ended Jan. 20. Gainers outpaced decliners 108 to 54, with 11 companies unchanged.

Among the biggest gainers was Guidance Software Inc., which jumped nearly 18 percent to $7.15. The Pasadena tech company reported a sharp increase in customers for its signature EnCase digital investigation product.

KB Home gained 8 percent to $9.31. The Los Angeles homebuilder benefited after a strong industry report.

Among the largest decliners was National Technical Systems Inc. The Calabasas provider of testing and engineering services fell 10 percent to $5.52, despite announcing a potentially lucrative strategic business alliance on Thursday.

Skechers USA Inc. fell 7.6 percent to $12.10, after an analyst downgraded the Manhattan Beach maker of athletic shoes and accessories.