When we say "Pro Wrestling," in America, I presume, it's honestly difficult to say. The most recent time period which is labeled as a "Boom Period" was powered by two major wrestling promotions battling it out, not merely to be #1 but to survive. The whole business from the mid-'90s through around 2001 or so was based on alacrity and trend-hopping.
However, it becomes difficult to quantify what we mean by pure "boom" periods if we're discussing WWE in particular. Their most financially successful year ever was 2007. And 2009 and 2010 thus far have both been very, very solid, despite a shaky economy that definitely hurt almost all avenues of entertainment, including WWE (live attendance has dropped a bit in the past six months or so and it's all due to the aftermath of the outbreak of the recession, but the outlook for the next six months or so is fairly good).
So, it's frankly hard to say when it comes to pro wrestling in general. I've spoken to a couple of indy promoters in California who thank God on a daily basis that WWE exists and remains as mainstream and positively strong as it does, because WWE remains the spectacle most young fans initially get into, and at least some of those young fans eventually want to find out what else is out there, like a kid who grew up on Indiana Jones Spielberg movies and then grows up wanting to watch Orson Welles classics and the latest Wong Kar-Wai picture. The whole "WWE's a monopoly and they'll never let anything rise up against it" line of thinking cuts both ways at the very least.
