Level of aggregation of zoning and temporal transferability of the gravity distribution model: The case of Lyon

Our findings confirm our initial intuition: the choice of zoning is fundamentally important. Moreover, in the best case, the parameters of the model change, but not sufficiently for the goodness-of-fit of the “predicted” model to be very different from that of the matrix obtained during calibration. It is possible to use the gravity model for forecasting purposes, but on condition that the goals of the study are compatible with the level of error in the reproduction of the observed matrices. If the zoning is either too coarse or too fine grained, forecasting performance is compromised.