The ABCs of ABS: Why the Address Based Sampling frame works so well

The past 10 to 15 years have been very good to Address Based Sampling (ABS). ABS has grown so much that it is now perceived as a substitute to random-digit-dial dual frame sample designs, and arguably, it has become the dominant sample survey design in the USA.

ABS is a special type of sampling frame, distinguishable from telephone surveys in its flexibility. The frame can support many methods and modalities: web, phone, and mail. In this article we will briefly explore the popularity of ABS and the problems it attempts to solve.

First, a quick historical lesson. Let’s look at what has happened to traditional telephone surveys. Response rates have tanked and many households have scrapped their land lines, forcing survey designers to sample both land lines and cell phone frames. To be fair, as recently as the late 2000’s telephone surveys were still doing rather well. They were still cost efficient and dual-frame survey designs (landline and cell phone) were gaining traction. While it is true that response rates were already in decline, data quality was not suffering.

The picture has changed in ten years. Telephone response rates have continued their precipitous decline (now down into the single digits) and associated risks of systematic bias have risen. Researchers have been forced to adapt by choosing alternative methods without sacrificing sampling integrity. ABS is a countermeasure for the trends we have witnessed with telephone response rates. The costs of telephone surveys have risen as well, compared to ABS. Not only has ABS solved some of those problems, it has opened the door to mixed modes of contact and data collection.

ABS from the ground up

The foundation of Address Based Sampling (ABS) is the United States Postal Service USPS Delivery Sequence File. Marketing Systems Group was one of the first companies to get approval for providing the Computerized Delivery Sequence (CDS) File, which contains just about every deliverable postal address. That’s more than 135 million residential addresses to date.

ABS merges the CDS with other data sources that contain geographic and demographic data. This is like cranking up the volume on your guitar amplifier to “11”. Data sources consist of both publicly available sources such as the Government’s American Community Survey, the Current Population Survey and decennial Census data. Beyond that, ABS can mine commercial databases for additional data.  You can append demographics such as age, gender, income, education, and more. By meshing data sources together, the odds for positive matches are increased and the negative impact of coverage lapses are decreased.  By targeting the household instead of the telephone number, ABS avoids the under and over coverage downside risks of telephone samples.

The difference maker: Geocoding.

Geocoding is the key ingredient which effectively launched ABS as a valid alternative. Geocoding is the application of geographical coordinates to a corresponding postal address location. Why does this matter so much? It means researchers can reach the majority of U.S. households more inexpensively and faster than ever before.

The basic geocoding method works like this:  addresses are coded using linear interpolation, constructing geographical data points within each street segment based on the numeric addresses as end points.  The interpolation is accurate to the street level but not necessarily to the actual rooftop level due to factors such as property size and park spaces. Still, you can get very accurate correspondences with geocoding.

There is no better approach for standard mail surveys as ABS has also solved problems with respect to in-person household surveys. Because CDS does not include census geography, it was a problem to design samples for in-person households. In the old days this was solved through costly methods: multi-stage sampling of primary and secondary sampling units based on census blocks and field-testing every address in a segment. ABS removes those obstacles. Every address is geocoded to a census block, with some exceptions such as P.O. boxes, rural routes, and simplified addresses (rural routes, P.O. boxes with no physical address). While it is true that simplified addresses are a nagging problem –the good news is that the scope of the problem has diminished: the number of simplified addresses, once upwards of 10 million addresses, has been reduced to the hundreds of thousands. Not insignificant, but a vast improvement.

In the past, ABS was hampered by some systematic nonresponse factors. For instance, ABS respondents were more likely to be college grads and less likely to be non-White, as compared to RDD samples. Lately however, mitigation efforts have made real progress due to Census data appends that can be used to predict areas of high nonresponse. You can oversample areas that tend to respond less frequently to ABS surveys. Consumer data also can be appended based on trackable behaviors and predictive models. This too can be used for oversampling nonresponsive areas.  In short, there are fewer reservations attached to the use of ABS, hence its increasing popularity.

ABS isn’t just a “one-trick pony”

To appreciate the raw power of ABS, you need to think of it as much more than its source USPS CDS file. It is an enhancement of it: CDS plus demographics plus geocoding. The effect is empowering. Researchers can increase the range of analysis options for testing hypotheses and models. And the ease of use has fueled the use of multimode surveys to combat the telephone survey problems mentioned above. ABS is also useful for probability-based panel recruitment, non-response follow ups, and for reaching more inaccessible populations with stratified samples. ABS gives you that flexibility. Samples can be drawn to custom specifications without sacrificing representation.

Key Advantages of ABS

  • Single frame. Does away with dual-frame uncertainty.
  • Expansive coverage.
  • Straightforward weighting protocols.
  • Higher response rates, especially when multimodes are used.
  • More precise.

For all the reasons mentioned above, ABS is proving to be the best balance between coverage and cost for many researchers, but we can only outline the many factors involved in a short blog article.

Call MSG today to discuss how ABS can be a difference maker in your survey research.

 

4 Surefire Ways to Increase ABS Response Rates Without Breaking the Bank

So you found the perfect sampling source with nearly 100% coverage and the ability to reach cell phone only homes with address based sample.  One can expect to get the completes needed but realistically what type of response rate will you achieve?  How can you boost it? Continue reading “4 Surefire Ways to Increase ABS Response Rates Without Breaking the Bank”

AAPOR ‘s Task Force on Address Based Sampling

In January of 2016, AAPOR ‘s Task Force on Address Based Sampling published it’s finding for the AAPOR Standard’s Committee.  MSG’s Trent Buskirk and David Malarek played a pivotal role in the formation of the ABS Standards.  Below is the Abstract for the report.  The full report can be found here: Continue reading “AAPOR ‘s Task Force on Address Based Sampling”

Harvard Case Study

MSG continually tries to build bridges to the academic and social science world by using long established contacts coupled with the will, desire and need to use its assets to assist in projects that serve the public good.  Frequently these projects involve project consultation, pro bona delivery of sample frame design and data or, as was the case with an MSG/Harvard University project a combination of all three.

In the Fall of 2014, the student’s in Professor Chase Harrison’s GVT 1010 Undergraduate Survey Research class undertook a multi-mode project to gauge the urban/suburban attitudes of residents in the Boston area.  MSG supplied not only the ABS sample but also allowed the students to consult with MSG personnel.  The result was a high response rate and statistically sound survey finding.  MSG would like to let all of academia know that we are available to work on select projects and can offer advice, suggestions and data if the project meets qualifications.

As Professor Harrison commented “MSG’s willingness to donate the sample for this project is just incredible.  I always encourage my students to use the best tools available, although I don’t always have the resources to help them use those tools, especially for things like general-population samples.  Thanks to MSG, this group was able to use a sample that otherwise would have been beyond their reach, and were able to experience what it is like to work on real-time survey with professional tools.”

Click Here for the full case study.