Another possibility is to look at the compensation for upper management. C-level officers are usually paid in stock as well as cash, but the staff reporting directly to them are salaried employees.

If you actually look at the graph (presented in the same article) it does not look like "the trend is reversing" at all. It rather looks like a very clear downwards trend with a strong cyclic component. So, when the times are good, the salaried bosses might just be handing out productivity bonuses to their reports, and passing the bill to the shareholders.