Excerpt from Forbes:
“In the six weeks since evasi0n was released, however, close to 18 million devices have already been jailbroken, according to data from Jay Freeman, the administrator of the Cydia app store for jailbroken devices. He says he’s counted 18.2 million unique devices running iOS 6 visiting Cydia, including 13.8 million iPhones, 3.4 million iPads, and 1.1 million iPod Touches.”
Considering only iOS 6 devices supported by Apple, the iPad 2/Retina/Retina-Lightning have sold over 100 million. Certainly many are running an old version of iOS jailbroken, but in general only 3.4 million out of ~100 million are jailbroken or 3%. Comparably, there are over 200 million iOS 6 compatible iPhone's out there...leading to about a 6% jailbreak rate.
Looks like those with an iPad Jailbreak are slacking off a little bit!