As far as i know, it's if more people are in same area, better will be the drop rate. For instance, if you kill Snipe alone, you have 5% chance to get a full loot (with x50 rate), and if few party come in same area then drop rate can up to 25%. It's how i understand how it works, maybe admin can explain better because they have algorithm (file). I highly doubt it would be like that since I can see how people can abuse that kind of system. You killing 1 mob & CP killing 100 mobs both have same set % chance, its just they killing 100 mobs faster gives them more shots to take the 5% chance where you only have 1 shot to take 5% chance. Them killing 100 mobs does not increase your 5% chance, your chance is still 5%. I agree that this is most likely purely subjective. When there is more people around, there is naturally more going on around, dragging your attention from actual hunting, making you less likely to "notice" you didn't drop anything, while a successful drop will always be pointed out to you by the sound and message. Conversely, when you are solo, the game quickly gets dull, and you count every minute and every percent of the grind. Only XP/SP gain is, in fact, affected by party size.