Oh the joys of stats which tell you anything you like.

Curious that the averages are from 87 to 99 when Chelsea were in the top division, making cup finals and winning trophies in the latter few years of that whilst City were languishing in the second division for a few of those years, winning nothing...wonder if that helps pad those figures up. And they were still only 6k less on average! Christ, what a useless set of average figures.
And why mention capacities? When the 90s came around and all stadiums had to become all seater, they both had there abouts 34k seater stadiums and have increased at different points in their history. So unless you want to work out %attendance of capacity for every year, it's a bit of a non-discussion point.(For the record, I worked out a few random dates from between 1970 to 1995 and actually City have a higher %, but shhh, don't let that spoil your stats)
Obviously both sides had inflated attendance figures when they started getting more success and obviously it grew as stadiums increased in capacity.
What you need to look at is the figures pre-success like 1970 to lets say 1995 when both sides were ****e, neither having any lasting success and neither having any sizable boost in income because that shows you which club has been the better support throughout all of its history - the hard times as well as the good times. Quick eyeballing suggests that actually City might have had a bigger average attendance looking at it that way before all of the success and money which was my initial point. Thanks.
Not really sure you understand how stats work, or you were more drunk than you thought.