Forecasting Mortality

IN a lecture to the Norwegian Actuarial Society printed in the Skandina?isk Aktuarietidskrift, Mr. Palin Elderton takes up the fascinating subject of forecasting mortality. Most medical statisticians and actuaries, if only for their private amusement, have tried their hands at prophecy. The most obvious line of approach, when rates of mortality in age groups are available over a long series of calendar years, is to take each group separately and to study the form of secular change, then, having more or less successfully represented the trend by some mathematical function, to extrapolate horizontally. As Mr. Elderton points out, this method would be inappropriate if changes in mortality at a later age are really determined by the experience through which the generation of which those at the later age are survivors have passed. In that case, one should consider not the horizontal but the diagonal progression of the table.