How they came up with the estimates of dead in Syria

"Applying a data mining technique called an alternating decision tree, Price, Ball and Jeff Klinger compiled basic fatality figures -- such as victims' ages, time and place of death -- from seven separate data sets, including those maintained by the Syrian government and opposition groups, including the oft-cited Syrian Observatory for Human Rights.  The names and vital details of 147,349 reported killings were then run through a computer program that is designed to detect duplicate references to individuals. The model was refined by a native Syrian Arab speaker who went through a sample of about 8,200 pairs of killings.  The figure was then whittled down to 59,648 "unique" deaths, though Benetech notes that it "was not able to differentiate clearly between combatants and non-combatants." The seven data sets used ranged from the Syrian government's record of 2,539 dead to more than 38,120 counted by the Violations Documentation Center, an opposition group. The larger number included in Pillay's estimate reflected the fact that the analysis was drawn from seven separate data sets." (thanks Narrima)