From the state of current knowledge, around 13 per cent of all treatments have good evidence, and a further 21 per cent are likely to be beneficial. This sounds low, but it seems the more common treatments tend to have a better evidence base. Another way of measuring is to look at how much medical activity is evidence-based, taking consecutive patients, in a hospital outpatients clinic for example, looking at their diagnosis, what treatment they were given, and then looking at whether that treatment decision was based on evidence.
