The morning has been good for the market. The Nasdaq is up 0.5%; the S&P 500 is trading up 0.5%; and the Dow has increased 0.4%. 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.

Outperforming the market overall, the Energy sector (XLE) is up 0.6% and its biggest movers so far today are:

Company Market Cap Percentage Change
NuStar Energy (NYSE:NS) $3.36 billion +5.1%
NuStar GP (NYSE:NSH) $1.15 billion +4.9%
Concho Resources (NYSE:CXO) $8.25 billion +2.9%
Helmerich & Payne, Inc (NYSE:HP) $5.36 billion +2.5%
CARBO Ceramics (NYSE:CRR) $1.73 billion +2.3%
Lufkin Industries (Nasdaq:LUFK) $1.79 billion +2.2%
Continental Resources (NYSE:CLR) $12.89 billion +2%

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Increasing 5.1%, NuStar Energy (NYSE:NS) is trading at $46.23 per share. This morning, the company is trading a volume of 590,783 shares.

Rising 4.9%, NuStar GP (NYSE:NSH) is currently trading at $28.70 per share. So far today, the company's volume is 264,796 shares, which is more trading activity than there was yesterday.

Concho Resources (NYSE:CXO) is currently trading at $80.36 per share, a 2.9% increase. The company's volume for the day so far is 267,614 shares. This is 0.3 times the current three-month average.

Helmerich & Payne, Inc (NYSE:HP) has risen 2.5% to hit a current price of $51.91 per share. The company's volume is currently 976,467 shares for the day, 0.6 times the current daily average.

CARBO Ceramics (NYSE:CRR) is up 2.3% to reach a current price of $77.18 per share. So far today, the company's volume is 44,151 shares.

Lufkin Industries (Nasdaq:LUFK) has increased to a share price of $55.07, a 2.2% rise. So far today, 71,231 shares have changed hands, while it was 382,818 shares yesterday.

Continental Resources (NYSE:CLR) is at $69.33 per share after an increase of 2%. So far today, the company's volume is 276,223 shares. This is 0.3 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.