Daniel Kahneman wrote his new book, a popular exposition of the behavioural economics research that won him a Nobel Prize, in part because he thought that popularizing some of the core concepts and allowing them to enter our vocabulary might improve the quality of our thinking and our public debate. Quite sadly I feel much the same about a lot of the basic concepts in economics and statistics that have been around a lot longer than behavioural economics. For instance, the core of impact evaluation; the counterfactual. Imagine what would have happened if the event we are examining had not happened. So let's imagine for a second what would be happening in South Sudan if there had not been independence. Peace and prosperity? New schools, roads, and hospitals? There are a couple of approaches we might use to think about what would have happened. We could look at the history of South Sudan pre-independence. We could look at all of the sterling development initiatives led by indicted war criminal Bashir in the South between 1989 and 2005. All of the schools and hospitals that he built. Or we could look at some of the people still living in the North. Perhaps those who have fled their homes to hide in caves from Bashir's bombers. Or the 100,000 who have fled to the South from Blue Nile. The counterfactual for South Sudan is not flowers and kittens, it is rule by a man wanted for five counts of crimes against humanity; murder, extermination, forcible transfer, torture and rape. Happy Birthday South Sudan.