98% of Affluent Americans use the internet

"IAB found that 98 percent of affluent consumers use the Internet, compared with 79 percent of the general population. Wealthy Americans spend around 26 hours online each week, 18 hours watching TV and about eight hours listening to the radio. The general population, on the other hand, spends about twice as much time weekly with TV and radio – 34 hours and 16 hours, respectively – and just about 22 hours on the Internet.
Other key data points show affluent users are just as capable of advertising recall. Eighty-eight percent of affluent consumers recalled being exposed to at least one digital ad during the previous week, compared with 84 percent of non-affluent Internet users. Within these groups, affluents recalled 21.1 ads on average, versus 20.2 for other groups."

Source:  Data from the IAB, reported by Venture Beat, 1st August 2011

Note - "The study defines “affluent Americans” as people with at least $100,000 annual incomes. They comprise 21 percent of U.S. households, have 70 percent of all consumer wealth, and spend 3.2 times more than other Americans on purchases."  (So that's household income, presumably)