[jsolson]

It's possible; without getting into specifics of any given company's compensation policy, one common compensation scheme involves cash + equity where the equity doesn't begin to vest until some tenure has been reached with the company. Let's assume base cash comp stays more or less constant (or has a some small raise to adjust for inflation).

Now, consider an initial stock grant that is 800 shares vesting linearly and monthly but with a one year cliff. If you started in January 2015 you would have seen zero of those shares in 2015. In 2016, however, you'd see 200 shares in January plus roughly another 200 shares throughout the rest of 2016.

If you also assume that the company in question provides annual stock refreshes, that those begin vesting immediately, and that the stock is on an upward trend it becomes apparent how such a large increase is possible.

Other factors could include non-salary cash comp like bonuses, etc.