Also a difference between city populations and the population controlled by the city council. Some councils, like Leeds cover a wide area other ones don't. Some, like Huddersfield don't have a town council. There will be a lot more people whose nearest club is City than there is Sunderland.
It is because it is a football city and didn't have rugby clubs for decades before a football one. What is there to do around Hull compared to Sunderland?
I was looking at this www.ukcities.co.uk/populations/ and this www.evi.com/q/how_many_people_live_in_city_of_sunderland. Also a list of most populous Built-up areas at the 2011 census showed: Sunderland Built-up area. Population 335,415. Kingston-Upon-Hull Built-up area. Population 314,018. Looks like a fair bit of variation!
With the signing of Juan Mata and the possible return of Rooney and RVP next week in the PL Cardiff City could well get roasted. Sounds good to me.
Population is one thing, but it comes down to the team being successful at the end of the day. You're forgetting the fact the Mackems used to win stuff, have been in the premier league/ first division a lot longer than us, & have appeared in cup finals. Their older generations have seen some moderate success- FA Cup in 73, FA Cup final runners up in 92, 85 League cup runners up. Doubt there's too many who remember their successful teams in the 30s. If our supporters had something like that to remember, rather than which chairman was the biggest twat, we'd have bigger crowds, and more people in the city would be prouder to support City.