One of Joy Global's mining machines. Image source: Joy Global, Inc.

What: Mining equipment maker Joy Global, Inc.'s (NYSE:JOY) shares fell 19.4% last month. But even after a nearly 20% decline, the stock was still up roughly 35% through the first five months of the year.

So what: Joy Global's business is inherently tied to the prospects of the world's mining industries. So, it shouldn't be much of a surprise that Joy's shares started 2016 off with a price drop, right along with the price declines seen for commodities. And then, in mid-January, the shares picked up again, along with the prices of the commodities that Joy's customers mine. In fact, between Jan. 15 and the end of April, the stock was up 125% or so, mirroring the gains of some of the world's largest miners.

Now what: Commodity prices go up and down, and that will, ultimately, impact the demand for Joy Global's mining equipment. That said, there's an oversupply in many commodity markets, miners are pulling back on growth projects, and while the early-year commodity rally was nice, there's likely a long way to go before you can call the "all clear" here. In fact, Joy Global's results are likely to remain relatively weak until capital spending in the mining industry picks up again in a meaningful and sustained way, something that will require better balance in the broad supply/demand equation than exists today for most commodities. In other words, investors should take any improvement in Joy Global's shares with a grain of salt.The commodity rally, however, took a breather in May. And so did Joy's shares, falling as much as 27% early in the month before recovering some ground. To make matters even more precarious, the company was set to release earnings results in early June. In other words, tensions were running a little high for shareholders of this equipment maker. (Although hardly a good reading, the June 2 earnings release showed that adjusted earnings were in the black -- a surprise to some industry watchers and a show of strength for Joy.)

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