This is a snippet of my stats output for BIND v9.3.4:

+++ Statistics Dump +++ (1219647723)
success 15541
referral 0
nxrrset 1316
nxdomain 1317
recursion 18661
failure 110

These numbers leave me scratching my a bit.

Shouldn't caching of look-ups always leave the "recursion" value being
less than the number of look-ups? (Unless every domain resolved is
unique, of course.)