Headline: The number of adults living in households with landlines has decreased in the past two years. Key Finding: The decrease is not yet significant, although it is a development to watch and monitor. Currently, nonresponse bias is a bigger issue than the drop in number of adults in households with landlines. Bottom line: A VALS-typed data set confers advantages for handling and evaluating nonresponse bias.

A variety of recent research findings indicate that landline-phone coverage of the adult population is on the decline. Such findings have sparked debate about how best to represent the adult population in research, given that the gold standard has been to contact people through landlines by means of random-digit-dial methodology. Such findings have also been the impetus for overblown claims about who is over- or underrepresented among landline, cell-phone, and Internet universes.

This paper focuses on two sets of benchmarks: who is currently included or covered in landline, cell-phone, and Internet universes and how well the landline, cell-phone, and Internet universes represent the adult population from a VALS™ perspective. After reviewing the benchmarks, we discuss trends and factors that influence coverage—that is, the kinds of people in these universes—and survey participation. The paper closes with a discussion of how well samples of people from landline, cell-phone, and Internet universes represent the total U.S. adult population and the VALS groups. The messy issue of nonresponse bias—the bias that comes in when the selected people to participate in research do not participate—is in the discussion.

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Table of Contents

Coverage of the Adult Population from a VALS™ Perspective			2
Trends and Factors that Influence Coverage			4
	Noncoverage of Landlines for the Adult Population		4
	Combined Landline and Cell-Phone Coverage		5
	Internet Access and Internet Connections		7
	Nonvoice Applications		8
Lack of Coverage and Implications for Bias			9
Conclusions			12
Tables
VALS™ Comparison of Adults with Landline, Cell-Phone, and Internet Access			3
Adults in Households with No Landline			5
Select Coverage Scenarios			6
Modem and High-Speed Internet Connections in the Home and Outside the Home			7
Comparison of Lower-Resource VALS™ Groups With and Without Internet Access: Net Agree			10
Comparison of Lower-Resource VALS™ Groups With and Without Internet Access: Mostly Agree			11