During and immediately following a myocardial infarction, care providers routinely explain the role of statins as a way to reduce the chance of further coronary events and even death. Hospitalised and recalling their recent chest pain, patients are usually highly receptive to this idea of taking a statin medication every day. Some may be reassured that clinical guidelines, supported by large clinical trials, give statins their strongest level of evidence.1 Physicians who follow these patients in clinic might conclude that statin use is widely adopted and well maintained, but these physicians could not possibly know for sure. Statins are among the most effective of medical therapies, but our ability to know if they are actually being used remains severely limited.

Into this information gap steps researchers who are able to find and follow the ‘entire denominator’—every patient in a country that has received care for an acute coronary syndrome. The paper by Grey et al2 is an excellent example, and tells the story of New Zealand's experience delivering statins to acute coronary syndrome (ACS) survivors in fine detail. Using a national data system that links public hospital records, outpatient pharmaceutical claims and death certificates, they were able to identify almost every ACS patient in their country and follow their pharmacy purchases for 3 years. This retrospective analysis included a cohort of over 11 000 individuals, most of whom experienced a non-ST elevation myocardial infarction (MI) or …