Wouldn't be at all surprised if Thorpe (and Chessie)'s sharp percentage rises in attendance were due to very poor performances the previous year... Looking quickly, Thorpe dropped 10% in 2012, so in the long run, does this increase really mean much? Considering that the poor performance couldn't directly be attributed to the park completely...
Towers dropped 9.4% the same year, Smiler helped in some respect, though of course the issues with the ride would have prevented a high rise... Imagine CBeebies Land will cause an even sharper influx this year...
Like, 11% of 2 million is 220'000, so that's 11 days worth of 20'000 guests... I find that using percentages to prove an arguement never fully tell the true story, as parks like Lightwater could in theory have a 45% increase in guest numbers but that might equate to something like an increase of 5'000, which isn't exactly much...