By looking at the past, strategic forecasters can learn lessons for the future. Long-term trends are the stock in trade of companies like Stratfor. And yet, as forecasters know perfectly well, sometimes things just seem to happen. The best-laid plans, backed up by analysis of reams of data, can be rendered obsolete by what the academic Nassim Nicholas Taleb, in a book of the same name, famously called a black swan: "an event, positive or negative, that is deemed improbable yet causes massive consequences."...