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

In what amounted to the first day of widespread bearishness of the young year, investors sold off heavily in the stock market today. Seizing on data from China showing a contraction in its manufacturing sector, Wall Street was easily spooked and dismissed corporate America's earnings -- which have largely been in line -- as an afterthought. The S&P 500 Index (^GSPC 0.03%) fell 16 points, or 0.9%, to end at 1,828. 

Johnson Controls (JCI 0.29%), the auto-parts maker, slumped 4.4% today, even though it announced earnings that exceeded expectations in the most recent quarter. Why would Wall Street, in its infinite wisdom, go out of its way to punish a company like Johnson Controls, fresh off a great quarter? Because you're buying a company's future -- not its past -- when you invest in any particular stock. And Johnson Controls painted a dimmer view of the future than shareholders would've liked. But it's hard to say that a 45% yearly bump in net income, which is what the company expects to achieve in its next quarter, demonstrates a floundering company. Clearly expectations were unreasonable in their own right.

No stranger to this list, Cliffs Natural Resources (CLF 0.95%) lost 4.3% today. Its most recent troubles stem from a Morgan Stanley note highlighting potential risks in a joint project with a China-based steel company, Wuhan Iron & Steel. The two companies are jointly developing a Bloom Lake iron ore mine in Quebec, but Wuhan has apparently begun slowing its payments to Cliffs Natural Resources, sparking fears that it could pull out of its partnership altogether. It certainly doesn't help that this news broke on the same day China showed weakness in the manufacturing sector, so keep an eye on China-dependent companies moving forward. 

Finally, Pitney Bowes (PBI 0.53%), which provides various goods and services to businesses to facilitate communication, saw shares fall 3.7% today. If you're a big believer in "reversion to the mean," then today's decline may be indicative of something larger. Stock in the company, fresh off a 120% return that made it one of 2013's best S&P performers, is down marginally so far in 2014. Pitney Bowes is a volatile stock and consumer goods was a beleaguered sector on Thursday, so its slump may simply be due to widespread bearishness and stymied momentum.