Factors in Vassalizing and annexing

[Secret Master]

Can anyone tell me the precise factors involved in successful vasalizing and diplo-annexing of countries? I ask because I've heard only general remarks about the chance of success and failure. I assume monarch skill is a big factor, as are having the pre-requisite relations and conditions (royal marriage, allaince, etc). But what are the specifics the AI uses to determine the chance of success?

 

[hjarg]

It is a bit random event as well: you can always reload and offer again and sooner or later they will prolly accept it. But to increace chances (here comes list of different rumours i have heard. Some may be untrue)

kings diplo value is very important factor
so is stability of both nations
treasury is said to count as well
not to mention size of troops
some even say placing troops in their border helps
naturally, size of your two nations counts as well- no one wants to be vassal of nation basically the same size he is
if nations was just unsuccessful at war is said to help as well
and one more important factor: pure luck