I don't do forecasts or predictions. Indeed, the strategy work I've done using Scenario Mapping / Future Mapping consciously avoids making forecasts, preferring instead to consider alternative and divergent outcomes and what would have to happen for each outcome to become reality.
Nevertheless, I've almost always liked Forecaster / Futurist Paul Saffo's work. His recent article on Six Rules for Effective Forcasting in the Harvard Business Review is no exception. The article is short, accessible, and to the point, so I won't try to summarize.
One idea and ensuing discussion concerns Rule 5: "Look Back Twice As Far As You Look Forward:"
So when you look back for parallels, always look back at least twice as far as you are looking forward. Search for similar patterns, keeping in mind that history—especially recent history—rarely repeats itself directly. And don’t be afraid to keep looking further back if the double interval is not enough to trigger your forecaster’s informed intuition.
The hardest part of looking back is to know when history doesn’t fit. The temptation is to use history (as the old analogy goes) the way a drunk uses a lamppost, for support rather than illumination. That’s the single worst mistake a forecaster can make, and examples, unfortunately, abound. Jerry Levin, for instance, sold Time Warner to AOL in the mistaken belief that he could use mergers and acquisitions to shoulder his company into digital media the way he did so successfully with cable and movies. He ended up closing the deal just when AOL’s decade-old model was being wiped out by new challengers with models allowing them to offer e-mail free of charge. Another case in point: A dark joke at the Pentagon is that the U.S. military is always fighting the last war, and indeed it is evident that in the case of the Iraq conflict, planners in certain areas simultaneously assumed that Iraq II would unfold like Iraq I and dismissed Vietnam as a source of insight because the U.S. had “lost that war.”