The Nasdaq is down 0.8%, the S&P 500 has decreased 0.2% and the Dow has declined 0.1%, marking a bad morning for the market.

The Oil and Gas Operations sector (DIG) is down 1%, underperforming the market overall. The current biggest movers in the sector are:

Company Market Cap Percentage Change
EnCana Corporation (NYSE:ECA) $15.5 billion -3.7%
Tesoro (NYSE:TSO) $5.81 billion +2.9%
HollyFrontier (NYSE:HFC) $9.19 billion +2.8%
PDC Energy (Nasdaq:PDCE) $960.9 million +2.3%
AmeriGas Partners (NYSE:APU) $3.57 billion -1.9%
Plains Exploration & Production (NYSE:PXP) $5.83 billion +1.7%
Rosetta Resources (Nasdaq:ROSE) $2.2 billion +1.6%

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After a decline of 3.7%, EnCana Corporation (NYSE:ECA) has hit a share price of $20.29. The company's volume for the day so far is 2.9 million shares.

Tesoro (NYSE:TSO) has risen 2.9% to hit a current price of $42.54 per share. The company's volume is currently 1.7 million shares for the day, in line with the current daily average.

HollyFrontier (NYSE:HFC) has moved up 2.8% and is currently trading at $46.48 per share. The company is currently trading a volume of 823,300 shares. This is 0.3 times the average volume over the last three months.

After rising 2.3%, PDC Energy (Nasdaq:PDCE) is currently trading at a share price of $32.47. So far today, the company's volume is 209,648 shares, lighter than yesterday's volume of 623,178 shares.

AmeriGas Partners (NYSE:APU) is currently trading at a share price of $37.75, a 1.9% decline. The company is currently trading a volume of 100,165 shares.

Plains Exploration & Production (NYSE:PXP) has increased to a share price of $45.94, a 1.7% rise. At 1.5 million shares, the company's volume so far today is 0.1 times the current daily average.

After an increase of 1.6%, Rosetta Resources (Nasdaq:ROSE) has reached a current price of $42.60. So far today, 128,741 shares have changed hands. This is 0.2 times its current three-month average.

The Bottom Line No matter the economic climate, Wall Street will always have stocks that make major moves each week. 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.