One reason why Andrew Mason held onto his job as Groupon CEO for long, we were told, was that he had the support of employees—and ousting him would crush morale.

That no longer seems to be the case, according to Glassdoor, the jobs and careers site which lets employees rate their bosses.

While Mason has a 57% rating based on all reviews, Glassdoor has shared data with Business Insider that shows that average ratings have plummeted in less than a year's time from 71% in the second quarter of 2012 to 39% today.

In other words, more than half of Groupon employees rating the company on Glassdoor recently had a negative opinion of Mason. (There's an obvious self-selection bias here, since the reviews are not from a random sampling but from employees who choose to review Mason, but that applies equally to the period when employees had a positive view of him.)

Here's the chart:

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