Amazon provided a lot of value to its shareholders in 2015. The company’s stock grew an astonishing 119% over the course of the year, making it one of the hottest stocks in the S&P 500 and the Nasdaq. But with a forward price-to-earnings ratio of 120.05, just how sustainable is Amazon’s run and what can we expect from the stock in 2016?

Earnings? What earnings?

Amazon has been notorious for favoring investment over earnings. Despite the company regularly increasing quarterly revenues by 20%+ year over year, it has rarely posted a quarterly profit. In 2014, for example, it posted a $241 million loss on the year. That’s not exactly what you’d expect from a company as mature and successful as this one.

If you take a look at 2015, however, it seems as if CEO Jeff Bezos and the management team are turning over a new leaf. While the first quarter of the year came with a $57 million loss, the second and third quarters saw gains of $92 million and $79 million, respectively.

Amazon Web Services, or AWS, seems to be the biggest driver of Amazon’s new-found profits. And with two profitable quarters in a row and continued exponential growth in AWS, it appeared to investors that the big payoff has finally come and they flocked to buy up Amazon shares.

But unless Amazon can show growing profits from its other business segments this year, AWS isn’t likely to be enough to keep the momentum going for the stock. That might be a problem, however, considering Amazon loves to sell its flagship products at or below cost and offer free shipping to its most loyal customers.

Will shareholders turn on it again?

For those excited about the prospects of Amazon turning 2016 into another great year, take a look at how the stock did in 2014. Fueled by investors finally losing their patience with Bezos and his invest-first mentality, the stock dropped 22% on the year.

Like any other stock, this one largely moves based on investor sentiment. But unlike other stocks, Amazon hasn’t historically had the fundamentals to back it up. Thus, the stock is more susceptible to the whims of irrational people.

Conclusion

Amazon is and always will be at the forefront of innovation in retail and e-commerce. But even with all the money the company spends to keep and gain new customers, investors can trust that Amazon can turn on the profit spigot when it’s time.

That said, it’s uncertain when that time is going to be. If the recent past is any indication, it’s unlikely to happen anytime in the short term. But even if Amazon’s shareholders are generally more patient than most, the year 2014 proves that even their patience has a limit.

That said, it’s unlikely we’ll see a repeat of either 2014 or 2015 this year. With AWS still growing and driving profits, there’s no reason why Amazon’s shares would tumble. At the same time, the incremental profit growth won’t be enough to merit another 100%+ year.