This is an example of a misleading image, and the false use of statistics. Medicos know errors happen and there are internal systems in place to notify critical incidents. These are confidential. They have to be confidential. Because if they are not, the ambulance chasers get hold of them and doctors spend time with lawyers preparing defences, or lose their privileges, or simply go fishing.

Because of the litigious nature of our society, we don’t have good numbers. We cannot do surveys. We can try to limit events, but this is a best guess. It could be wildly out. Our suicide and road crash data is much more robust.

We calculated a mean rate of death from medical error of 251?454 a year using the studies reported since the 1999 IOM report and extrapolating to the total number of US hospital admissions in 2013. We believe this understates the true incidence of death due to medical error because the studies cited rely on errors extractable in documented health records and include only inpatient deaths. Although the assumptions made in extrapolating study data to the broader US population may limit the accuracy of our figure, the absence of national data highlights the need for systematic measurement of the problem. Comparing our estimate to CDC rankings suggests that medical error is the third most common cause of death in the US

There are some risks with this. Most of the time, medicos get things right. They are motivated to get things right. Some times there are errors: hospitals are complex systems, generally run by with a paucity of staff apart from the administrators. Running continuous audit and root cause analysis is expensive.

What we do know is that tired staff make more errors.

And that blaming staff for being irritable and grumpy and error-prone, when you have large demands and no interest in protecting them — which is all too often the case — saps morale, increases distrust, and increases error. For it is not about the US system: there is some data that the NHS is far worse.

We need ways and means of measuring error and learning from others. The surgical checklist is an example of how to limit mistakes. But to err is human. And hospitals are a human institution.