MK by year:
2020= 6,941,000
2019= 20,963,000 - another good year
2018 = 20,859,000 - a good year!
2017= 20,450,000 = up .25% from 2016, but still 42,000 fewer people than 2015
2016= MK fell .5% to 20,395,000
2015 = 20,492,000
2014 = 19,332,000
2013 = 18,558,000
2012 = 17,536,000
2011 = 17,142,000
2010 = 16,972,000 = down 1.5%
2009 = 17,233,000
2008 = 17,063,000 =flat
2007= 17,060,000
That's as far back as I could easily find.
[Just as an aside - Theme parks overall were down a whopping 67% percent last year. Increases are usually like 1-2%, so that's pretty stunning.]
When I searched for 2002, I found MK at 14,044,800, which was supposedly down 5% from 2001 (= not the same report). Epcot was down 8%, US was down 6%, but IoA actually went up10% in 2002. A side note says this is because Halloween Horror Nights was moved from US to IoA that year. Asia had a strong 2002; Europe was a bit mixed. Disneyland CA was able to mitigate a decline in travel by offering deep discounts to CA residents. Vegas' Circus Circus increased attendance that year by offering free admission. (source: Amusement Business Magazine via
www.csus.edu)
So that supports what I posted above. When advance bookings go down, theme parks can improve actual attendance by offering discounts, sometimes deep discounts. Attendance is only part of the picture.