In the U.S. in the first half of 2009, 22.7% of households had only wireless telephones. Another 14.7% of households received all or almost all calls on a wireless phone. The share of wireless-only households has increased 2.5 percentage points in only six months.
More rapid shift to wireless telephony among younger persons isn’t surprising. Among persons ages 25-29, a total of 64% lived in wireless-only or wireless-mostly households in the first half of 2009. Young persons do not want a shared phone. They are unlikely to shift back to a shared (wireline) phone as they get older.
Large differences in the share of wireless households across states are more difficult to understand. Some impressive statistical work constructed state-level estimates for wireless households in 2007. This work found “great variation in the prevalence of wireless-only households across states … ranging from a low of 5.1% in Vermont to a high of 26.2% in Oklahoma.”
Differences in state demographics, household characteristics, and wireless subscribership per capita apparently don’t explain considerable variation across states. A logistic regression of wireless-only/wireline-phone-present households controlled for age, sex, race/ethnicity, household poverty status, home ownership status, other demographics, and state-level wireless subscribership per capita. State-level wireless subscribership per capita was identified by its variation across 2007 within states. Within this regression, state fixed effects vary considerably. For example, Texas had a 16 percent point higher wireless-only household share than California would have at Texas’ levels of the control variables. Wireless telephony is not regulated at the state level, but wireline telephony has been regulated at the state level since its beginnings. Perhaps some of the state-level variation in wireless-only households reflects state-level variation in wireline-phone offerings.
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 Blumberg SJ, Luke JV. Wireless substitution: Early release of estimates from the National Health Interview Survey, January-June 2009. National Center for Health Statistics. December 2009. Available from: http://www.cdc.gov/nchs/nhis.htm
 Blumberg SJ, Luke JV, Davidson G, Davern ME, Yu T, Soderberg K. Wireless substitution: State-level estimates from the National Health Interview Survey, January-December 2007. National health statistics report; no 14. Hyattsville, MD: National Center for Health Statistics. 2009, p. 2.
 Id., Table II.
 For my calculation of the significance of the state fixed effects, see the state factor worksheet.