post by Paul Kelleher
Matthew Yglesias recently wrote:
The way modern business works, a wide range of retailers charge you less if you swipe a loyalty card so they can engage in some nefarious data tracking schemes.
And here's Kevin Drum a few years ago:
I really loathe retail loyalty card programs. Really really really.
And here are members of the Wisconsin Division of Public Health and the Wisconsin State Laboratory of Hygiene who in 2006 investigated an outbreak of E. coli O157:H7 infection:
We conducted a shopper card investigation to refine the data we were getting with regard to the products of concern. Case patients were asked for their shopper card number and whether they would permit the Wisconsin Division of Public Health to review their purchase history. A major grocery chain in Wisconsin (which includes multiple brands in their stores) provided a list of all purchases made with participants’ shopper card numbers during the 4 weeks before the respective illness onset. Purchase histories were compared with self-reported consumption. [...]
Of the 27 case patients with available shopper card information, 17 (63%) purchased brand A spinach; of these 17 case patients, 2 (12%) had shopper card information that indicated a purchase of brand A spinach, but they had not identified a brand during their interviews. The concordance of recalled information with shopper card information was not associated with age. Of the 15 case patients who had shopper card information that indicated purchases of a specific brand of spinach and who also recalled during their interviews a specific brand of spinach they consumed, 14 (93%) purchased the same brand of spinach that they recalled consuming. The 1 case patient whose recollection differed stated in her interview that she only consumed brand D spinach, but her shopper card information only indicated a purchase of brand A spinach. [...]
An environmental investigation conducted by the FDA and the California Department of Health Services identified E. coli O157:H7 isolates with a PFGE pattern indistinguishable from the outbreak pattern in samples obtained from river water, cattle manure, and wild pig feces in and around a field used to grow brand A spinach with the P227A product code. Beginning with Wisconsin’s recognition of this outbreak, the rapid response of the public health system in Wisconsin and nationally...and the cooperation among many partners permitted FDA officials to quickly announce a broad national alert regarding fresh spinach and, within 15 days, to narrow the focus of environmental investigation to spinach that was processed by a single company and grown in 3 California counties.
Of course, currently this public benefit of shopper cards is purely ancillary to the shopper's own interest in saving a few cents here and there. But notice one interesting thing. If a private lab finds E. coli in the stool of ill patients whose clinicians have ordered tests to determine the illness, the lab is required (in some/many/most/all? states) to send the E. coli isolates to a state lab for DNA testing. This testing allows state investigators to draw links between seemingly unconnected illnesses. And if I understand this correctly, the state has the power to do this DNA analysis on the stool of a private citizen* without his or her consent (and maybe even without telling him/her about it)---all in the name of public health. And yet when shopper card information would be equally helpful, state investigators are required to ask patients for their shopper card number "and whether they would permit the Wisconsin Division of Public Health to review their purchase history." How quaint.
*It is true that the DNA analysis is done on the DNA of the E. coli bacterium, not on the DNA of the person's whose stool the E. coli was found in. Good luck explaining that distinction to the American public.