Geographic variation in the use of medications: is uniformity good news or bad?

Studies have repeatedly found much geographic variation in use of surgical and diagnostic procedures. This study of the variability of medication use for specific conditions in eleven California regions finds surprisingly few differences among regions. The difference between the highest- and lowest-use areas was far less than we anticipated and amounted to only 30-40 percent for many drugs. We explore five potential explanations for low geographic variability: financial incentives, impact of managed care, study design elements, characteristics of California, and pharmaceutical marketing and education efforts. To determine whether these findings represent good or bad news will require further study.