RTI International’s Address-Based Sampling Atlas: Drop points
The Computerized Delivery Sequence (CDS) file contains listings for nearly all addresses in the United States. Survey researchers use the CDS as a sampling frame from which to draw an address-based sample (ABS). More than 700,000 addresses on the CDS are marked as drop points, which are mail receptacles shared by multiple housing units (drop units). Drop points are a challenge to sample and present a potential source of error because of their "one-to-many" relationships. Several techniques have been developed to overcome this challenge, including deleting them from the frame or sampling all units at a given drop point. This paper serves as an introduction to these challenges, discusses the pros and cons to each "solution," and provides a list of best practices.