effects of ai difficulty settings ?

[Boron]

i just always want to know this with every game i play
what are the special benefits the ai gets at difficult / impossible settings ?
plz list them all if possible
do they simply get a multiplier on income , research and so on like difficult x2 and impossible x3 or are there other benefits too ?
and on what do they get the multipliers ?
do they perhaps get additional points in pretender design too or can build more than 1 capital only leader per turn ?
thnx for the info