This morning Pew is out with new tablet and e-reader numbers: 50% of US adults now have one or the other or both. In particular 42% of Americans 18 and older own tablets (still mostly iPads but also Kindles).
Using these figures, by my calculation, there are now 102 million tablets owned by US adults. There are plenty of kids that have them too so the actual number is larger — perhaps by 20 million or more.
Comscore says that smartphone penetration is now 64% in the US mobile market. Nielsen puts the number at 65%. That’s more than 150 million smartphones.
Pew also reports its survey data reflect that 75% of US adults own PCs (desktops or laptops). That works out to about 181 million adults with PCs or a vaguely equivalent number of machines. (Some people obviously own more than one PC so the number may be somewhat larger).
These figures are somewhat imprecise. However it’s safe to say that that when we combine tablets (102 million) and smartphones (150+ million) we have a total of approximately 250+ million mobile devices in the US (not counting those under 18).
Accordingly there are roughly 70 million more mobile internet devices than PCs in the US market. Boom.