US mobile-only households are now 22.7% of the total population according to the US CDC. Arbitron has compiled an interesting map showing what that actually looks like geographically (in Arbitron radio markets). We’ll continue to see landlines disappear to the point where by 2015 roughly 40% – 50% of US households may be mobile only.
This trend has a number of implications, including for the directory assistance (DA) industry. Increasing percentages of 411 calls come from mobile phones. As people adopt smartphones, DA calls decline — because people have access to the mobile Internet and specialized apps that provide more information and greater control over information.
Below is a graphic of the Arbitron map:

You can download the map from the Arbitron site (linked above).