It's hard to compute non-base compensation precisely, because stock price is inherently volatile, especially over four years. If your vesting schedule includes absolute numbers of shares you will receive in 1, 2, 3, 4 years, you cannot possibly predict the value of those shares, and therefore cannot reliably measure your per-year compensation.
For example, if you knew four years ago that you would receive 30 GOOG stock in 2016, you would assume in 2012 that would mean a $10k bonus. But now the stock has gone from $325 to $754, the bonus is actually $22k.
If you work for a company with an increasing stock price, then stock based compensation can also create the illusion that your "salary" is increasing each year, even if you get no promotion.