RTI Press Publication

RTI International’s Address-Based Sampling Atlas

Drop points


Amaya, A. E. (2017). RTI International’s Address-Based Sampling Atlas: Drop points. (RTI Press Publication No. OP-0047-1712). Research Triangle Park, NC: RTI Press. DOI: 10.3768/rtipress.2017.op.0047.1712


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.


Ashley Elaine AmayaAshley Amaya, PhD, is a research survey methodologist in RTI International’s Survey Research Division.

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