Crowd counts are an interesting thing, and lets look at long term history.
Disneyland started to care the year they opened in 1955, when they got overwhelmed with guests, and Walt placed limits on ticket sells that first summer. So Disney started a department (well, back then it was two CM's, who also had other duties) that started to look at main factors and ways to get info. Te found out the school schedules and holidays had a main impact, and they could get info from nearby location. They didn't own any Hotels, but they were working with those nearby, so deals were made, hey, give us your advance reservation numbers and in return we will let you know the "trends" and what we decide what is coming up. Also, places like Knott's, in which Walt and his senior staff worked with in the 50's before Disneyland opening studying traffic patterns, so they also started to share. Universal and SeaWorld also joined the info sharing in the 1960's when they started operating.
When the Walt Disney Travel Company was formed, Disney found out they could now get a lot of trend information in what folks were buying and when, things like rooms,sizre of the group, how many days they planned to attend, etc. Plus they started to get good information in past history in the late 50's after a couple of years of operation.
Nowadays, we have a strong sharing system in Southern California of Hotels, attractions (and not just Theme Parks), and even major restaurants that come up with some pretty good numbers and trends (including average spending).
The Hotel/Lodging business in general has also formed a company that tracts the numbers and makes predictions.
Harrison "Buzz" Price was hired by Walt Disney in 1953 to study past history and figure out the best location to build,focusing on the "center" of Southern Californi in regards to potential customers. Buzz formed ERA (Economics Research Associates) in 1958, and that was the basis of what is now known as the best research for Amusement Park numbers on a daily and yearly basis. (The researchers basically is known as TEA/AECOM currently).
Now, to be honest, Disney has different set of numbers and each set has a different level. The most basic one is what Disney leads and CM's are told to help staff and predict things like what items to order to handle the expected crowds. Not too specific, but any insider can get a hold of them. The next level is Management,and is what is also known to outside sources, but attached is a NDA,so supposed to be kept quiet and not released to the public. I used to remember debating a TDA manager, who got online with the screen name "Marcie". She hated the fact I was given better numbers than she got, which prevented her "spin" from being challenged back in the early 2000's. And there are even more specific numbers that go to upper-level management,and is shared by the big players, think senior management of other Theme Park Companies, etc. And they know that the better they share, the more specific they are. But still, there is part of the companies that keep a little info to themselves, just human nature.
I know some of the websites that do the predicting, one of which, Touring Plans, I have a history with through the Unofficial Guides. They have access to many of the numbers mentions, bit not the highest level. But then the numbers come in different periods, long term advance, short term advance, and then the next day forecast. That is the hardest one to get ahold of, and also has impacts in regards to the current day sales and actual attendance, and the weather forecast.
Computers are also helping gather more info and trends, and also help in sharing the info in easy transfer of info. (I remember get the faxes with the numbers).
So yes,things do change, and well, in this case, the need to revisit the "scale" and adjust them due to changes in the trends and actual numbers.
I am still involved, but my info is basically the filming and airing of specials and live TV remotes, like morning news programs. If one of those airs promoting a specific park and its new attractions, you will see a spike in attendance for that location over the short term. Also they want to make sure they are timed to avoid two being done at the same time.
Hope that bit of inside info helps....