US consumers generally enjoy
widespread Internet access. While the Web was once the playground of
affluent early adopters, the demographic profile of the US Internet
user now resembles that of most Americans.
Nonetheless, about one-quarter of Americans have no Internet access…

Nonetheless, about one-quarter
of Americans have no Internet access, according to a wide-ranging
report titled "Information Searches That Solve Problems: How People Use
the Internet, Libraries and Government Agencies When They Need Help" by
the Pew Internet & American Life Project and the Graduate School of Library and Information Science at the University of Illinois at Champaign-Urbana.

US Adults Who Have Internet Access, by Access Technology, June-September 2007 (% of respondents)

For marketers working on multimedia campaigns, knowing who the
non-users are can help determine media buys—and avoid wasting Web
efforts targeting consumers who will never get the message.

Pew said that those with limited access or no access to the Internet tended to be older, less affluent and less well educated.

Demographic Profile of US Adult Internet Users, by Access Technology, June-September 2007 (% of respondents)

The organization also studied the demographics of those with "low access," meaning either no access or only dial-up access.

When dial-up users were added in, demographic differences fell away.
In other words, the low-access group had similar characteristics to
Internet users as a whole. As the researchers put it, "demographic
predictors are evident only within the 24% of those with no access at
all."

Pew’s data lined up quite closely with that of other
researchers. Pew’s US broadband penetration number of 55%, for instance,
is close to eMarketer’s 2007 estimate of 53.6%.

Internet Users and Broadband Households in Select Countries Worldwide, 2007 (millions and % of total)

Via eMarketer