In the first quarter of 2012 the average U.S. mobile subscriber used 450 MB of data per month, according to research firm Nielsen. That figure is more than double the average of 208 MB per month for all U.S. mobile subscribers in the first quarter of 2011. The usage statistics, provided exclusively to FierceWireless, come from data in monthly cell phone bills of at least 65,000 mobile users who volunteered to participate in the company's ongoing research. Nielsen did not break out the average monthly data usage among U.S. smartphone owners (the company's figures cover both smartphones and feature phones). However, between the first quarter of 2011 and the first quarter of 2012, the nation's smartphone penetration rate went from a significant minority to half of all U.S. mobile subscribers. The focus on average usage is particularly noteworthy now, since Verizon Wireless (NYSE:VZ) has launched share data plans and AT&T Mobility (NYSE:T) will do so next month. Both plans allow customers to share a pool of data among multiple people on a single account, allowing, say, family with higher data usage to share a bucket of data with those with lower data usage.