Bias in List-Assisted 100-Series RDD Sampling

Abstract

List-assisted Random Digit Dial (RDD) sampling methodology was developed decades ago when local telephone exchanges relied on 100-series telephone banks as physical building blocks. In recent years, however, the telecommunication industry has undergone a number of fundamental changes including a complete transition from analog to digital call routing and departure from an AT&Tdominated infrastructure to what is provided by regional independent operating companies as well as a growing number of alternative landline service providers. Combined with the decline in the proportion of directory-listed households and dilution of the residential landline assignment density due to a sharp increase in the number of residential exchanges, these changes have all but eliminated the utility of 100-series banks for frame construction and sampling purposes. In spite of the above drastic changes, the sampling frame construction methodology for RDD samples has changed very little (if any) over the years. This note provides an overview of a research conducted to reexamine the underlying assumptions that were conducive to list-assisted RDD sampling against the ground realities of today. Specifically, the extent of undercoverage bias in traditional RDD samples is quantified while alternative methods of frame construction are introduced that aim to restore some of the lost coverage. Proposed alternatives are evaluated in light of cost implications that can result from adoption of more inclusive sampling frames, since such expansions will inevitably require additional resources for sample designs and survey administrations.