Complex sentence: The percentage of the U.S. population using the Internet grew steadily through 2007, declined slightly in 2008 and 2009, growth resumed in 2010, and reached its highest level so far (81.0%) in 2012, the latest year for which data is available.
Split into simpler sentences: The percentage of the U.S. population using the Internet grew steadily through 2007, and declined slightly in 2008 and 2009. Growth resumed in 2010, and reached its highest level so far (81.0%) in 2012, the latest year for which data is available.