PROPELLED BY A BURGEONING MARKET in downloadable music and videos, U.S. consumer spending on content surged to $2 billion in 2005. This marks a 15 percent increase from 2004, according to new research by the Online Publishers Association. Subscriptions continued to be the most common pricing model, accounting for 78 percent of total revenue. But revenues from single purchases, such as music downloads, continued to grow. Last year, single purchases accounted for 22 percent of content revenues, up from 15 percent in 2004.