I find this data point from the BLS rather intriguing:
In 2001, the ratio of spending on residential phone services to spending on cellular phone services was greater than 3 to 1. In 2007, cellular phone expenditures accounted for 55 percent of total telephone expenditures compared to 43 percent for residential phone expenditures.
Data from the Bureau of Labor Statistics’ Consumer Expenditure Survey (CE) show that cellular phone expenditures increased rapidly from 2001 through 2007. Cellular phone expenditures surpassed spending on residential landline phone services beginning in 2007. Chart 1 shows that annual expenditures for cellular phone services per consumer unit increased from $210 in 2001 to $608 in 2007, an increase of 190 percent. Expenditures for residential phone services per consumer unit decreased from $686 to $482 over that period, a decrease of 30 percent.
Spending on Cell Phone Services Has Exceeded Spending on Residential Phone Services