MP3 vs Ogg
This determines how many MP3s and how many Ogg's I have...
Then we can tell how popular each format is according to my harddrive...

Results:
mp3 = 167 	14% 612 MiB 	16%
ogg = 992 	85% 3 GiB 	83%
Total = 1159	99% 3 GiB 	99%

(Rounding errors can happen...)