Thank you, agbd, for that interesting reference. I tried to understand it, though it seems that apples are being compared with oranges.....gliders mainly collide with other gliders (that sounds about right). But this survey which covers collisions over a period of 37 years, doesn't say which were fatal collisions.
It is possible to have a very respectable crash in a glider, writing it off, and still walk away. It is also true that we fly wearing parachutes, which in case of a midair can come in handy. I really don't want to have any sort of crash in a light aircraft carrying any quantity of fuel whatsoever.
It is far from clear whether this study includes gliders bumping into other gliders on landing. We did have at our club a truly interesting arrival when a solo pilot landed the club twoseater on top of TWO other gliders, both were unoccupied at the time. And a famous former chairman managed to land his glider on a boat that was being towed by a landrover, how do you classify that one? And famously, a pilot from another club landed their two-seater in the wrong place and was plowed into by the cable retrieve vehicle; didn't have time to stop....the pilot's remark clearly heard by the observers was "O no, not again!"
But usually we do manage to land with sufficient self-separation to avoid damage.