ON THE SENSITIVITY OF GRAVITY MODEL FORECASTS*
提出一种估计重力模型预测对输入值微小变化的敏感性方法，可推导协方差矩阵以构建置信区间和假设检验，尤其适用于双约束模型和大规模起讫点区域。
ABSTRACT In this paper we present a procedure for estimating small changes in gravity model forecasts in response to small changes in input values (trip end totals and/or parameter values). The procedure can be used to derive covariance matrices from which confidence intervals may be obtained and which may be used for tests of hypotheses. While this type of problem has been addressed by others, our approach is the only one that is conveniently applicable to the doubly constrained model and can accommodate the large numbers of origin and destination zones one typically encounters.