U.S. online sales rose 12 percent from a year before in the first three months of 2011, their fastest pace of growth since before the 2008 financial crisis, according to research firm comScore. Online retail spending reached $38 billion in the first quarter, with the 25 most popular online retailers making up 67.7 percent of those sales.

ComScore said the rise was fed by a growing number of people shopping online and more visits to online stores. But the average size of online transactions fell 4 percent. ComScore chairman Gian Fulgoni said rising gasoline prices had prompted some shoppers to go online rather than to actual stores, helping online sales grow about twice as fast as in-store sales. The last time online sales grew 12 percent or more was in the second quarter of 2008.