Saints have done ok, excluding the Stobart year they averaged 9,842 in SL, when they have often been a very successful team. Since they moved to Langtree their average has increased 27% to 12,455 (source: rugbyleagueproject).
Considering the fact that they were already pretty engaged with much of the town due to the amount of success they had enjoyed, that is a very good increase. I think where it may be interesting is if Saints become a mid-table team will the crowds drop off. It is easy to stand in a rubbish ground and justify it when your team is winning, when the team is poor we see real drops, I believe a decent stadium protects some of this drop off as the overall event is more attractive.
I do think Hull's move has been extremely successful, even if it was just bringing back lapsed fans. Their last 15 years at the Boulevard in the top flight saw an average of 5,693, their move to KC Stadium has seen them more than double that to 11,760 over the last 10 years. That is undoubtedly a stadium success story.
Sorry Dave, bit of a rushed post at lunch time. What I was trying to get over is that there is a perception about the new stadium affect that is an exaggerated one.
Some of the headline increases either aren't real increases or are exaggerated, as in Saints case, by the season before the move being exceptionally poor.
In 2005 Saints averaged almost 11k, now when you compare what has happened that 27% suddenly drops to 12%. I don't blame clubs for finding ways to push the headline figure higher, but, lets not get carried away thinking Saints have 27% more supporters than when they were at KR. Wigan have no more, apart from one season than they were averaging at CP Pre SL.