Governments and independent experts have found countless metrics to evaluate the successes and failures of military interventions such as those in Kosovo, Afghanistan and Iraq, judging them on everything from casualty rates to the provision of public services. The number of girls attending school in Afghanistan, for example, has been a standard point of reference for supporters of the NATO mission there.
But what metrics can be used to evaluate a deliberate nonintervention?
This question is grimly relevant to assessments of the West’s decision not to take military action in Syria to date. Advocates of an intervention have a lot of data to support their argument. This January, the United Nations estimated that the civil war had already claimed 60,000 lives, a much higher figure than it had previously cited. There have been cases, including Kosovo, where death rates in civil wars were greatly overestimated. But the U.N. figure for Syria is widely accepted. The number of Syrian refugees that have fled to neighboring states is easier to calculate with some certainty: It is currently more than 700,000 and rising fast.