Should traps have tells?

[Bill Zebub]

Depending on how one writes one's adventures, the PCs could easily hit 50 traps over the course of their careers. If the expected casualty rate due specifically to traps is an aggregate 33% over that time, if the party averages six PCs that means over the long run traps will kill two of them.

In terms of what that means for this thread, of whether traps should have "tells":

To achieve that 33% kill rate...killing 2 out of 6 PCs after 50 traps...each trap would have to have an efficacy of less than 1%.