Statistically, how are you more likely to die doing Everest-- going up or going down?
However, how “dangerous” it is may not be strictly correlated with how many climbers die going in each direction. According to that article, most traumatic injuries (falls, avalanches) occur on the lower slopes of the mountain. The majority of deaths, however, are non-traumatic and due to exhaustion, lack of oxygen, etc. Those may be due primarily to the length of time spent in the “Death Zone,” so of course will mainly take place on the return, after climbers have spent a lot of time at the highest elevations.
I would imagine that’s not so much because descending is more dangerous than ascending in and of itself, but rather because adverse circumstances are more common during a descent.
Only the true fools choose to begin a summit bid in the middle of a storm. From what I understand, though, it’s alarmingly easy to find yourself caught in one after you’ve started up - which requires that you make your descent through it.
When climbers run into trouble ascending a mountain, one common reaction is to retreat. So you’d expect more accidents while descending.
(Which is sort of what brad_d said.)
Does “falling off” count as “descent”? That might explain some of it too.
In the many books I’ve read on the subject (and reading is about as far as I’ll get to climbing such a mountain), they all state “When you reach the top, you’re only half done, and the hard part is yet to come.”
They indicate that the downward trip is the most dangerous for a multitude of reasons. First, you’ve been hiking upwards for quite a while, and often fueled by anticipation and “get-there-itis” (a common problem in general aviation accidents as well). When you’re on the way down, you are already tired, perhaps past the point where you’ll have sufficient oxygen to complete your return trip. Weather may have changed during the ascent portion, or even during the descent. Additional energy may have been spent, or need to be spent to assist your climbing companion(s).
I’d also say that based on my experiences with local day hikes, the descent phase of walking is much harder to achieve stable footing due to both an unnatural leg extension, and visibilty. Both of which are made worse on a mountain like Everest due to clothing, goggles, and oxygen equipment.