According to this article (and info-graphic) at ArtNews:
Recently The New York Times cited Skate’s Art Market Research in an article on the slowdown in the growth of art fairs worldwide. In an analysis of attendance figures, Skate’s found “that 1,032,792 people attended the world’s top 20 art fairs in 2014, a 7.4 percent decline from the previous year,” The Times reported. Despite the dip, art fair attendance is impressive, given that only a handful of these events have existed for more than a decade.
What I find interesting is that many people will go to more than one fair – especially the ABMB / Art Miami numbers are curious. I’m assuming there is a ton of overlap between those two. However, with fair attendance decreasing but sales increasing (or at least sales numbers increasing) I think we are a long way off from seeing the art market change it’s current stance on the necessity of fairs overall.