Petrobas Among Energy's Biggest Movers on December 19, 2012

The Nasdaq is trading up 0.1%, the S&P 500 has decreased 0.1% and the Dow has remained steady so far today. The energy sector is the category of stocks that relate to producing or supplying energy. This sector includes companies involved in the exploration and development of oil or gas reserves, oil and gas drilling, or integrated power firms. Performance in the sector is largely driven by the supply and demand for worldwide energy. Energy producers will do very well during times of high oil and gas prices, but will earn less when the value of energy drops. Furthermore, this sector is sensitive to political events, which historically have driven changes in the price of oil.

The Energy sector (XLE) is unchanged so far today and here are its biggest movers:

Company	Market Cap	Percentage Change
Western Refining (NYSE:WNR)	$2.71 billion	-5.5%
YPF SA (NYSE:YPF)	$6.22 billion	-5.4%
Gulfport (Nasdaq:GPOR)	$2.19 billion	-4.4%
Petrobas (NYSE:PBR)	$127.38 billion	+4%
Bonanza Creek Energy (NYSE:BCEI)	$1.08 billion	+3.7%
Bill (NYSE:BBG)	$974.1 million	-3.1%
PDC Energy (Nasdaq:PDCE)	$1.06 billion	-3.1%

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Western Refining (NYSE:WNR) has fallen 5.5% and is currently trading at $28.96 per share. At 601,246 shares, the company's volume so far today is on pace to finish the day below yesterday's volume of 1.9 million shares.

At $14.96, YPF SA (NYSE:YPF) has slipped 5.4%. This morning, the company's volume is 974,746 shares. This is in keeping with its current daily average.

Currently trading at $37.66 per share, Gulfport (Nasdaq:GPOR) has fallen 4.4%. So far today, the company's volume is 4.6 million shares, 4.3 times its average over the past three months.

Petrobas (NYSE:PBR) has increased to a share price of $20.32, a 4% rise. So far today, 11.6 million shares have changed hands.

Bonanza Creek Energy (NYSE:BCEI) is currently trading at $27.88 per share, a 3.7% increase. The company's volume is currently 208,852 shares for the day, lighter than yesterday's volume of 624,142 shares.

Bill (NYSE:BBG) is trading at $19.60 per share, down 3.1%. The company's volume for the morning is 470,888 shares. This is in keeping with its current daily average.

PDC Energy (Nasdaq:PDCE) is down 3.1% to reach $33.84 per share. At 204,612 shares, the company's volume so far today is 0.2 times the average volume over the last three months.

The Bottom Line The nature of the market is such that stocks will have good days and bad days. Paying close attention to the previous ratios will help you identify key times to adjust your strategy. Tools like valuation ratios and profit margins, however, are only as useful as the context you put them in; remember to take historical data and competitor performance into account.