Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Stock markets are closed today to observe Martin Luther King Day, but we're setting up for a busy weel on Wall Street. As fellow Fool Dan Caplinger pointed out earlier today, there are eight companies in the Dow Jones Industrial Average (INDEX: ^DJI) reporting earnings this week. Markets haven't had a lot of catalysts so far this year, so earnings will be important. Last year's market was driven by earnings-multiple expansion, with the Dow's P/E ratio rising from 15.1 to 17.0 over the past year. This year, investors are expecting more earnings growth, so the next week will be key.

Globally, China announced today that GDP grew 7.7% in the fourth quarter, down from 7.8% a quarter earlier. Industrial production was up 9.7%, also down from 10% growth in November.

Slower growth in China will have a negative effect on demand for oil, and now that Libya's exports are picking up, there will be increased pressure on margins for oil explorers. It's a double-edged sword for ExxonMobil (NYSE: XOM) and Chevron (NYSE: CVX), which may make more money on refining, but will make less profit on exploration and production if the price of oil falls.  

Libya has already increased oil production from 220,000 barrels per day in late 2013 to 600,000 barrels now. When combined with slowing growth in China and decreasing oil demand in developed countries, it's easy to see why oil has fallen below $94 per barrel and could fall further.

China and India are the only two major countries keeping demand for oil from falling and if their growth slows it'll be terrible for oil demand. You can see that global demand growth for oil has been slowing, and the U.S. and Europe are actually using less oil than five years ago.

World Oil Consumption Chart

World Oil Consumption data by YCharts.

At the same time, prices at the pump have topped out, and consumers don't appear to be willing to pay ever more for gasoline. All of these factors point to a tough fourth quarter for ExxonMobil and Chevron and worsening trends in 2014.

ExxonMobil reports earnings on Jan. 30 and Chevron weighs in the next day, so keep an eye on where upstream and downstream margins are headed and where management thinks demand will grow next year. The macroeconomic trends are working against big oil companies, and that could make for weak earnings and guidance.

How should you play energy now?
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Fool contributor Travis Hoium has no position in any stocks mentioned. The Motley Fool recommends Chevron. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.