The thing about these numbers and rankings is that they're unofficial and unverified.
The TEA does not actually see the real figures from any theme park company. From what I heard Len Testa and Sam Gennawey saying (theme park guidebook/history book authors), TEA guesstimates the numbers ... based on what I don't know. Then they show the numbers to the theme park companies and ask them, as a favor, to "comment on them". Meaning, please either tell us they're correct or provide us with the correct numbers.
And - the authors seem to consider this to be a significant fact - supposedly they show the numbers they intend to publish to Disney Corp last, after the other companies have seen and possibly corrected the numbers.
Now it would be expected that TEA would only show each company their estimate for that company's parks. But the authors expressed some suspicion that the numbers are not completely accurate and the process might be skewed. One of them implied that certain companies may be shown the other companies' numbers, presumably as an inducement to get the company to participate.
This is only repeating hearsay, and implied hearsay at that ... but these authors were definitely scoffing at some of the things in the report. Especially the relative rankings of certain parks.
You can see that there is some motivation for some companies, some of the time, to make their numbers look better than they really are. A company that has invested a lot in new attractions would want everyone to see that the investment paid off. A company that has been slacking off and not building new attractions would want to let it be known that they still have great, market-leading numbers. Not that the public are a bunch of dumb sheep or anything, but ... everyone loves a winner. So do investors.