After attending a party, pawns are given an "Attended Party" mood boost. I've noticed though that there's a multiplier next to the attribute, like "Attended Party x4", and they get a mood boost that seems to be around 75% the value of the multiplier (they get a 3 point mood boost with a "x4" multiplier).
I know the multiplier isn't how many parties they've attended because I know my guys haven't thrown, for example, 4 parties within 10 days (the expiry period of the buff). It seems to be a "quality" indicator.
What effects the multiplier? Number of social interactions? Time spent at the party? And is there a reliable way to ensure higher multiples?