The S&P 500 Index (SNPINDEX:^GSPC) eased back from its record closing high on Friday, ending slightly lower after surprisingly weak trade data from China sent a shiver down the back of Wall Street. Expecting Chinese exports to rise by nearly 7% in February, they instead fell by more than 18%, betraying an unforeseen softness in the world's second-largest economy. The stock market pulled back briefly in January after Chinese manufacturing data disappointed, but today's numbers didn't spook investors quite as much, and the S&P 500 fell by less than 1 point, or 0.1%, to end at 1,877. 

Cliffs Natural Resources (NYSE:CLF) was the most miserable stock in the whole index today, losing 3.8% in trading. The success of Cliffs Natural, although based in Cleveland, is closely tied to the ups and downs of China's economy. As one of the largest steel producers in the world, China relies on Cliffs Natural and other companies that produce iron ore and metallurgical coal, two necessary inputs in steel production. This is where Cliffs' lack of diversification plays against the company; expect shares to remain high-risk gambles as long as China is able to singlehandedly impact commodities prices so dramatically. 

Shares of another coal miner, Peabody Energy (NYSE:BTU) shed 3.7% Monday. As goes China, so go many coal and commodities plays, and with China's poor showing today, Wall Street had very little to be excited about in the coal industry. Peabody Energy specifically is also still suffering from a sudden move to shake up its executive team, an announcement that sent the stock plunging more than 5% on Friday. Coal in general is not an area I'm attracted to as a long-term investment given the increasing focus on cleaner, alternative forms of energy, but the days of a worldwide sustainable energy ecosystem are still decades away, so until then coal's not as doomed as it's made out to be.

Finally, shares of security provider ADT Corporation (UNKNOWN:ADT.DL) dropped 2.8% on Monday, as the stock proved unable to shield investor portfolios from losses. Top-line growth at ADT has slowed from over 20% in 2011 to less than 3% in 2013, a troubling trend that, should it continue, implies that cost reduction is the only way to grow net income. ADT does reward investors, however, for putting their money behind a slow and steady business, as its dividend currently sits at 2.6%. From a long-term perspective, the "Internet of things" could prove to be a game-changer in the home security market, and if ADT can't keep up, software firms that allow you to monitor your house through an app may pose an imposing threat to the traditional model.