today i started counting..
at the moment 51 cards are on my list as "expired" , meaning, travelling about a year.
since may last year, so about the same period, 1207 of my cards registered.
i know.. not exact science.. but indeed.. slightly over 4%
juicy side note.
that card i sent out exactly a year ago, was sent to someone who's been not online for 4 months.
(the one to Germany's nr 1 postcrosser expired as well.. so activaty is not allways the key factor)