According to a new study (pdf) by Nielsen, 17.1 percent of Americans (about 20 million of us) have ditched their landline for wireless phone service only, a number that the stat farm says is rising at about three to four percent per year. The majority of users who've severed their landline are in lower income brackets (under $50k), tend to be younger (18-34), and have a smaller household size (1-2 people). Some assorted stats from the report:

•Wireless substitutors pay on average $6.69 more per month on wireless than those who retain wireless and landline service. Those users still save, on average, $33 per month per household, given that the average household spends around $40 per month on a landline (plus those notorious fees).

•10% of U.S. households with landline phone service used to be cell only, but switched back. 17% of those returning customers switched back because they had some device they believed needed a landline (DVR, security system). 11% switched back to get a bundle discount from a bell. 10% of them switched back because of poor voice quality.

•Cell only, users, on average, used about 1074 minutes per month, compared to the 742 minutes per month used by users who retained both a cell and landline.

•Cell only users are 16% less likely than the average person to have satellite TV, and 27% more likely to use over the air TV reception. They're also 62% more likely to have cable broadband, and 13% less likely to have DSL than the average household.