Last week, I criticized CEO Marissa Mayer’s draconian ban against working from home for all Yahoo! Inc. employees. As someone who has personally fought this battle, I am absolutely convinced that having the ability to work from home makes me far more productive and less grumpy. Without the arrangement, I might have quit my job years ago, and you wouldn’t be reading my rants. Think of the loss.

But as much as I’m an advocate for flexibility, I’ve always had a suspicion that there are career costs to working off-site.

Unfortunately, my hunch is right. According to a newly released study by Stanford and Beijing Universities, working from home benefits both efficiency and morale—but not the career prospect of the individual employee. The study finds that employees of a Nasdaq-listed Chinese travel agency who worked from home increased their performance by 13 percent and reported greater work satisfaction; this resulted in fewer turnovers. But here’s the downside:

"Their promotion rate conditional on performance fell."