The sales levels of anime adaptated from manga are basically a crapshoot. Not so much Light Novels. Though I still haven’t compiled at the 2012 data, but one particular bit of information popped out of the 2011 sample that it deserves its own individual mention. It’s best described as 2 rules of thumb:
1. No LN series that had at least one week where a volume sold 20,000 copies in that week (disregarding cumulative totals) that went on to sell less than 4000 disks per volume. Only one (Mayo Chiki) sold less than 5000.
2. No LN series without at least one week where a volume sold 20,000 copies sold more than 4000 disks per volume. Only one (Kore wa Zombie Desu Ka?) sold over 3000.