The Relationship Between the Length of the Base Period and Population Forecast Errors
研究了人口预测中基期长度对预测误差的影响，发现基期长度增加到10年可提高预测准确性，但进一步增加效果不大；仅对快速增长州的长期预测，更长基期能显著改善两种预测技术的准确性。
Abstract The base period of a population forecast is the time period from which historical data are collected for the purpose of forecasting future population values. The length of the base period is one of the fundamental decisions made in preparing population forecasts, yet very few studies have investigated the effects of this decision on population forecast errors. In this article the relationship between the length of the base period and population forecast errors is analyzed, using three simple forecasting techniques and data from 1900 to 1980 for states in the United States. It is found that increasing the length of the base period up to 10 years improves forecast accuracy, but that further increases generally have little additional effect. The only exception to this finding is long-range forecasts of rapidly growing states, in which a longer base period substantially improves forecast accuracy for two of the forecasting techniques.