either the 2nd or 3rd most popular US sport
More like 4th.
NFL, MLB, and NASCAR (if one wants to consider car racing a sport) are all ahead of the NBA.
This is however a very difficult thing to measure since the variables are very different in all of them.
You cannot do total attendance when one sport plays 81 home games, another plays 40, and another plays 8
You cannot do average or total attendance per game because one sport has arenas that hold 20,000 to stadiums that hold 40,000 to 50,000 to stadiums that hold 60,000 to 90,000
You cannot do total viewership combined because some sports have much more games televised
You cannot accurately compare viewership per game when most sports are regionally covered and play pretty much everyday (so each game is not as important) and another sport plays 1 day a week and is nationally televised (therefor more people at once make a special day to view on that one day)
The best thing to go by is playoff ratings since they all pretty much have national coverage. This is where we get:
- NFL
- NASCAR
- MLB
- NBA
- NHL
Football will always have the advantage because of the fact that that each team plays only 16 games (thus each game is more important), plays one day a week (so all fans get together at one time to watch or attend instead of getting together any day they choose), and their playoffs are one game each (one game in which everyone can get together at one time).
Throw in college playoffs and pretty much all of them move down (except NFL).