Source: Wikimedia Commons.

Investing is a global business, and news events from around the world have a major impact on the stock market. The European Central Bank's stimulus measures helped send stocks higher yesterday, while the death of Saudi Arabian King Abdullah bin Abdulaziz introduced new uncertainty in the energy sector. Yet even though markets are global, investors also have to keep their eyes squarely on the homefront, especially during earnings season. On Friday, U.S. markets were mixed, with the Dow Jones Industrials (DJINDICES:^DJI) falling 42 points shortly after 11 a.m. EST as investors tried to deal with the crosscurrents from disparate reads on the U.S. economy from several earnings reports. In particular, gains in coffee giant Starbucks (NASDAQ:SBUX) showed the strength of certain companies, while an earnings warning from shipping specialist United Parcel Service (NYSE:UPS) proved that not every stock has benefited equally from favorable economic conditions.

Source: Starbucks.

Starbucks jumped more than 6% to an all-time high as the company reported solid results for its fiscal first quarter. Revenue rose 13%, with comparable-store sales picking up 5% on an increase of nearly 12 million transactions during the quarter. The coffee king saw its best performance in the Asia-Pacific region, including China, which saw comps grow 8% from the year-ago quarter and revenue soar thanks to the company's acquisition of its Starbucks Japan unit. In particular, the company was impressed with its holiday-season successes, with CEO Howard Schultz saying that Starbucks' "reimagined in-store holiday experience ... resonated powerfully with our customers and drove both increased traffic and tremendous excitement in our stores and around the Starbucks brand." Given just how much room Starbucks still has to expand its footprint globally, investors clearly believe that the company is pursuing the right strategy to make the most of its opportunity.

Source: UPS.

On the other hand, UPS shares fell almost 10% after the shipping giant cut its guidance for its fourth-quarter earnings results. The company now expects to earn $1.25 per share for the quarter, blaming underperformance in its domestic shipping business. Even though UPS saw package volume and revenue come in close to what it initially expected, the company had to pay more in order to meet demand during the peak holiday season, costing UPS on the bottom line. After the previous year's hiccups, which resulted in late package deliveries on Christmas gifts, UPS spent a lot of money to make sure those problems wouldn't repeat in 2014. As CEO David Abney said, "Though customers enjoyed high quality service, it came at a cost to UPS," and CFO Kurt Kuehn said that initiatives to face up to the challenges of soaring e-commerce-related shipping volume could take years to play out fully.

Market participants should watch macroeconomic and geopolitical news to ensure they don't miss important market-moving events when they happen. But you also need to watch your individual stocks closely, as earnings and other company-specific news can have a much more dramatic impact on your investments no matter what the overall market is doing.