Interesting to compare with 2002 that's the year of highest attendance in the last 36 years at least probably over 40.
And stopping at 20 years misses the 16 years prior that the attendance is also up from.
Something else big that has been going on since the butt and rise of television is that the studios focus on really big movies to draw people to things they don't see on tv. So few movies that get a big draw, it's crazy how much of the market the top 10 movies made in the US and Canada last year. That trend might very well continue. With less of us seeing movies regularly the studios are counting on premium prices for the few movies that are seen with 3D Imax and in some places premiums for seats in the middle.