Predictions usually deal with events—who will win an election, whether or not a country will go to war, the specification of a new invention; they center on decisions. Yet such predictions, while possible, cannot be formalized, i.e. made subject to rules. The prediction of events is inherently difficult. Events are the intersect of social vectors (interests, forces, pressures, and the like). While one can to some extent assess the strength of these vectors individually, one would need a "social physics" to predict the exact crosspoints where decisions and forces combine.... Forecasting is possible where there are regularities and recurrences of phenomena (these are rare), of where there are persisting trends whose direction, if not exact trajectory, can be plotted with statistical time-series or be formulated as historical tendencies. Necessarily, therefore, one deals with probabili ties and an array of possible projections. But the limitations of forecasting are also evident. The further one reaches ahead in time with a set of forecasts, the greater the margin for error, since the fan of the projections widens.