Image source: Shake Shack.

When it comes to the IPO class of 2015, Shake Shack (SHAK 1.26%) may have been one of the more volatile freshmen. The gourmet burger chain went public at $21 in January, peaked at $96.75 in May, going on to shed more than half of its peak value as 2015 comes to a close.

I went over some of things that went right and went wrong in 2015. Now let's turn our attention to what 2016 has in store for Shake Shack and its investors. 

We know what Wall Street thinks. Analysts see revenue climbing 26% to $239.6 million as expansion (and to a lesser extent, improving comps) fuel top-line growth. They also see a profit of $0.39 a share, up 22% from the $0.32 a share that they are targeting for all of 2015. 

That's a healthy growth rate, but worrywarts will naturally flock to the price of Shake Shack stock relative to those forecasts, arriving at some pretty problematic multiples. With 36.3 million shares outstanding and Shake Shack stock just north of $40 as we head into the final trading week of 2015, we're looking at a stock fetching more than 100 times forward earnings and a forward sales multiple of 6.1 -- both clocking in well ahead of rival eateries. 

This doesn't mean that Shake Shack is cruising for a bruising in 2015, but it can lead one to dismiss the stock as overvalued despite trading within pocket change of hitting another new low. 

That would probably be a mistake. For starters, let's talk about those Wall Street bottom-line projections. Analysts have historically underestimated Shake Shack's earnings power. Let's go over its first four quarters as a public company.

Q4 2014 ($0.03) ($0.01) 67%
Q1 2015 ($0.03) $0.04 233%
Q2 2015 $0.03 $0.09 200%
Q3 2015 $0.07 $0.12 71%

Source: Yahoo! Finance.

We're not just talking about landing just ahead of where the pros are perched; Shake Shack is obliterating Wall Street's profit targets. This naturally finds analysts revising their forecasts higher. Over the past three months alone we've seen the earnings estimate for 2016 go from $0.31 a share to $0.39 a share. As long as Shake Shack keeps making analysts look like serial pessimists we're going to see that 2016 forecast jacked higher throughout the year. 

Shake Shack's sales multiple is also a bit thorny, but it's important to remember that Shake Shack owns most of its domestic restaurants. Bears that love to call the stock overvalued by dividing its market cap by the number of eateries -- stacking that up against larger burger flippers that are mostly franchisee-run operations -- are getting it wrong out of the gate. 

Shake Shack had just 41 company-owned burger joints by the end of the third quarter, pegging the market cap per unit at nearly $36 million apiece. That's rich, but you can't fairly compare that to the country's three biggest burger chains that own between 0% and 10% of their outlets. It also bears pointing out that no one is buying Shake Shack based on the past. It has gone on to open a pair of new Shake Shacks this quarter with plans to open at least 14 company-owned locations in 2016. That drops the multiple to a still-steep $26 million, but keep in mind that the future extends well beyond the next 12 months. 

It's been a successful year for Shake Shack stock if you measure its performance from the IPO price of $21. It's been a disaster if you chart it since its springtime peak. Float-broadening insider selling and valuation concerns didn't help, but fundamentally speaking, Shake Shack is solid.

It's not going to be as volatile in 2016 as it was in 2015. The wider float will make it harder to rock the stock one way or the other, and the breathtaking year-over-year comps growth -- up 17.1% in its latest quarter -- will be a thing of the past. Shake Shake's targeting a more modest 2.5% to 3% uptick through 2016. It's still hard to bet against Shake Shack now that it has spent the past seven months working off most of its excessive valuation. The ceiling is high for Shake Shack, and the prospects for the cult fave chain to beat the market in 2016 remain strong.