What: Joy Global's (JOY) stock price dropped nearly 21% last month, following an 18% drop in December. The shares were down more than 70% in 2015. It's been a tough slog, to say the least.

So what: The story hasn't changed at Joy Global: It is one of the largest manufacturers of mining equipment in the world, and the mining industry is struggling. So Joy and competitors like Caterpillar have been hard hit by an industrywide spending slowdown as miners retrench. The January decline is really just more of the same.

However, China remains a major influence on the market's perception of Joy Global, its competitors, and miners in general. Demand from a fast-growing China was the driving force behind the commodity boom that pushed miners to expand production. Now that China has started cooling off, there's a huge oversupply in most key commodities -- thus the slowdown in demand for mining equipment. But China's economy continues to show signs of weakness, which means the mining downturn, and the headwinds buffeting Joy Global, don't appear to be abating.

Now what: The mining downturn doesn't look like it's over, and Chinese growth remains a big trouble spot. Until supply and demand balance out, results at Joy and Caterpillar will likely be relatively weak. There will come a day when that changes, but right now it's hard to call the end to this commodity downturn. In other words, only contrarian investors should be looking at a company like Joy Global right now.