“Extrapolations are useful, particularly in that form of soothsaying called forecasting trends. But in looking at the figures or charts made from them, it is necessary to remember one thing constantly: The trend-to-now may be a fact, but the future trend represents no more than an educated guess. Implicit in it is "everything else being equal" and "present trends continuing." And somehow everything else refuses to remain equal, else life would be dull indeed.”