The S&P 500 increased a whopping 4.5% last week, reaching a new high for the year after the services sector showed some strength, retail sales gained for the first time in more than a year, and Alcoa (NYSE:AA) unofficially started third-quarter earnings season with some good news.

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

Winners:

Company

Percentage Gain

Micron Technology

18%

Massey Energy (NYSE:MEE)

17%

Office Depot (NYSE:ODP)

17%

Teradyne

17%

Hartford Financial (NYSE:HIG)

16%

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

Losers on the week:

Company

Percentage Loss

Ciena (NYSE:CIEN)

(12%)

MBIA (NYSE:MBI)

(10%)

St. Jude Medical

(10%)

Sprint Nextel (NYSE:S)

(8%)

O'Reilly Automotive

(4%)

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

A look at some of the movers
Hartford Financial gained after an analyst at UBS tacked a buy rating onto the insurance company. The analyst said Hartford Financial has sufficient capital on hand -- $9.2 billion -- to withstand future losses as well as adhere to potential capital requirements imposed by the government. The analyst further noted that if the stock market continues to climb, the insurer could produce greater earnings: Thirty percent of Hartford's earnings revolve around equities.

Communications equipment maker Ciena made a bid to acquire Nortel Networks' optical networking and carrier Ethernet assets for $521 million. However, shares of Ciena slipped on the news after a UBS analyst raised concerns about the risks associated with the potential acquisition -- notably intensive integration efforts that could weigh on operations and an increase in debt levels that could shift Ciena's balance sheet to net debt. Nortel, a Canadian networking products and service provider that's in bankruptcy, is selling off its assets.

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Fool contributor Jennifer Schonberger does not own shares of any of the companies mentioned in this article. Sprint Nextel is an Inside Value pick. The Motley Fool has a disclosure policy.