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.

After logging a sleepy session on Monday, the Dow Jones Industrial Average (DJINDICES:^DJI) looks set to open higher this morning. Stock index futures as of 7 a.m. EDT pointed to a 0.29% rise at the start of trading. World markets ticked up as the Japanese Nikkei index rebounded from the loss it posted yesterday on weak economic data. European stocks improved to near three-month highs.

U.S. markets could see volatility spike today as trading volumes continue to dip. With most companies having already reported their second-quarter earnings, and with a light economic calendar ahead, the dog days of summer have descended on Wall Street. Yesterday, for example, less than 5 billion shares were bought and sold across the U.S exchanges. That was low enough to qualify as one of the five least active trading days of the year, according to Reuters.

One stock that could see heightened interest in a sleepy session today is Yum! Brands (NYSE:YUM). The fast-food chain reported a surprising 13% drop in comparable sales in China, including a 16% decline at its KFC stores. That fall was nearly double the 7.1% dip that analysts expected. Yum! Brands is still dealing with the fallout of intensely negative press regarding the quality of its poultry supply chain that came up late last year. Considering that China is responsible for more than half of the company's operating profit, investors have good reason to worry over any sign that the dip in KFC sales may prove long-lived. Shares are down 3.5% in premarket trading.

Dow component Alcoa (NYSE:AA), meanwhile, looks set to continue its recent outperformance. The stock has found plenty of buyers over the last few trading days as economic data, particularly in China, points to a global economy that is steadily improving. Alcoa is up 2% over the last month, versus a 0.3% drop in the Dow. Commodity prices continue to inch up, and that's good news for the aluminum giant.

Finally, high interest in shares of Apple (NASDAQ:AAPL) could continue into a second day, as the company's extended lull in new product announcements appears to be ending. Tech site AllThingsD reported that a redesigned iPhone is due for unveiling next month. And while it isn't the iTV or the iWatch (or the iCar) that many investors have been anticipating, the iPhone still holds enormous potential for Apple's business. The company sold 31 million units last quarter, which was 20% better than in the year-ago quarter. A refreshed iPhone offering could be enough to maintain that impressive growth rate, even in the face of intense competition.

Fool contributor Demitrios Kalogeropoulos owns shares of Apple. The Motley Fool recommends Apple. The Motley Fool owns shares of Apple. 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.