Not long ago, critics were declaring TV comedies dead, with most sitcoms lacking both ratings and laughs. But comedies have been undergoing a renaissance over the past several years. Fresh, smart series like The Office, Glee, and Modern Family are becoming hits with viewers and critics alike. This year, sitcoms are smashing ratings records. And so far the only new fall shows to get full-season pickups have been comedies. What's behind the sitcom surge? Here, six theories:

1. They're easier to watch
Comedies have math on their side, says CBS executive Kelly Kahl. An episode of a sitcom like New Girl is a half hour long. Reality shows like The X Factor, The Biggest Loser, and American Idol sometimes run up to four hours of programming a week. That's "a big commitment." On the other hand, "comedies are nice little entertaining packages."

2. With more comedies on the air, some are bound to be hits
"Success breeds imitation," says Josef Adalian at New York. Programmers look at the success of a show like Modern Family and decide they want a piece of that pie. So more sitcoms are getting green-lighted and put on the air. "Everyone's trying it because it's working," says Richard Weitz at Variety. With so many comedies to choose from, it's a virtual certainty that some will emerge as huge hits.

3. Comedies have become more innovative
While there is innovation and freshness behind recent comedy hits like Glee, Modern Family, and New Girl, there's a "tired familiarity" to many of the new dramas and reality shows, says David Hiltbrand at the Detroit Free Press. Charlie's Angels is a remake, The X Factor is almost exactly like American Idol, and The Playboy Club and Pan Am blatantly rip off Mad Men. "Why are you putting on a show that references girdles," says media consultant Shari Anne Brill, "when all of us have moved on to Spanx?"  

4. People want to laugh in these hard economic times
In tough times, people need a good laugh, says Mark Dawidziak in the Cleveland Plain Dealer. Comedy ratings have risen in down economies throughout TV history. We're seeing a veritable "Occupy Prime Time," says James Poniewozik at TIME, as the working-class frustrations underlying the Occupy Wall Street protests find their way into popular new sitcoms, such as 2 Broke Girls, The Middle, and Raising Hope. "It's a step back toward the '70s, when producers like Norman Lear made sitcoms about dockworkers (All in the Family) and even actual poor people (Good Times, Sanford and Son)."

5. They haven't been overhyped
The "hysteria that surrounded the premieres of The X Factor, Terra Nova, and The Playboy Club" was inescapable ahead of the fall TV season, says Lisa de Moraes at The Washington Post. Yet those shows debuted to underwhelming numbers, while comedy series — both new and old — surged to record ratings. The hype only magnified the fact that "younger viewers who decide what's hot and what's not have given up on trying to find the next Lost and have cooled on reality competition shows."

6. TV trends are cyclical
There's no "grand logic" to be applied here, says Adalian. Whether the trend is reality TV, sitcoms, or medical dramas, "it's just a matter of finding the right balance" in the menu of programs networks put into their schedules. Comedies aren't on the rise because the economy is down — do people not enjoy laughing during boom times? — or because today's shows are particularly innovative — Zooey Deschanel may be unique, but top-rated Two and a Half Men is "just The Odd Couple with more erection jokes." TV is cyclical, and it just so happens that we're in the "Year of the Comedy."

Sources: Detroit Free Press, New York, Plain Dealer, Time, Variety, Wash. Post