Spatial heterogeneity between pharmacies was observed, with some having more or less substandard drugs (30% and 0% respectively), as was product heterogeneity, with some drugs being more or less frequently substandard (12% and 7% respectively).
http://plosone.org/article/info:doi/10.1371/journal.pone.0006003#article1.front1.article-meta1.abstract1.sec2.p1

Interesting observation from a well designed and executed study, thanks.

It is well known in India among reasonably informed people that certain pharmacies are better than others, and certain brands are better than others when it comes to buying drugs. It is quite common for people to frequent specific pharmacies and build a trust relationship with the pharmacist(s) to avoid problems associated with sub-standard drugs.

It would be interesting to couple this study with a qualitative/semi quantitative survey/study of people buying drugs, and how they choose pharmacies/drug brands.

It would also be important to look for urban/rural, and income divides.

Improving overall quality will help everyone including the not so well informed or well connected consumers. This is as much a social justice issue as it is a quality issue, as the poor and rural populations will have less pharmacy choice, fewer brand choices and much less information.