We can look at the Conference trends in a graphical format below. Note that 1997 was an unusual year in that it was the largest SIGGRAPH Conference and so can sometimes obscure the trends.
Exhibition space has been declining since it peaked in 1997, but we expect that S2001 will be greater than S2000 and will reverse the trend.

The total Technical attendance (Full Conference plus Conference Select) has been rising steadily since 1994.

The total Conference attendance has been fairly steady, with a very marked West Coast vs. Non-West Coast effect. This is because the total attendance is dominated by the exhibits plus attendees, who tend to be local..
