After a volatile week, the S&P 500 ended last week flat at 1,106.41, marking the fourth week in a row that the market has pretty much traded sideways. News last week that served to gyrate the markets included Moody’s threat to downgrade the U.S. and U.K. from AAA ratings on deficit concerns. On the flip side, ongoing jobless claims were revised lower, and the trade deficit unexpectedly narrowed in October.

Pops and drops
Here are the five biggest S&P 500 upticks and five biggest S&P 500 drops of last week (measured Friday close to Friday close):

Winners on the week:

Company

Gain on the Week

Gannett (NYSE:GCI)

28%

Interpublic Group

14%

Alcoa (NYSE:AA)

12%

UnitedHealth Group (NYSE:UNH)

11%

Cigna

11%

Source: Capital IQ (a division of Standard & Poor's).

Losers on the week:

Company

Loss on the Week

Kroger (NYSE:KR)

(11%)

Ciena

(9%)

Kimco Realty (NYSE:KIM)

(8%)

SUPERVALU (NYSE:SVU)

(8%)

Wynn Resorts (NASDAQ:WYNN)

(7%)

Source: Capital IQ (a division of Standard & Poor's).

A closer look
Kroger had a rough week after the grocery-store chain turned in a worse-than-expected fiscal third quarter and lowered its full-year outlook for the second time this year. Kroger swung to a loss in the quarter, thanks to a $1.05 billion writedown on its California-based division, Ralphs; intense price competition among other grocers; and falling food prices.

On the other hand, Gannett had a strong week. The newspaper publisher and owner of USA TODAY said that advertising sales are picking up across classified, online, and retail categories. The company also said circulation is picking up and that it expects greater improvement overall in 2010, but that the economy is still fragile.

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Fool contributor Jennifer Schonberger does not own shares of any of the companies mentioned in this article. UnitedHealth Group is a Stock Advisor and Inside Value pick. The Motley Fool owns shares of UnitedHealth and has a disclosure policy.