Exponential or Power Distance-Decay for Commuting? An Alternative Specification
Environment and Planning A, Vol. 41, No. 2, pp. 461–480
Posted: 2 Oct 2009
In this paper we investigate the functional form of distance decay for commuting flows between municipalities in Denmark. Our inference is based on a single equation that includes variables to capture the effect of spatial structure. Special attention is given to a proper estimation method: We estimate the distance-decay parameters by nonlinear weighted least-squares with balancing factors. It appears that neither an exponential nor a power distance-decay function fits the data well. Using a spline regression we find a cost elasticity of -4 for distances around 20 km and a much smaller value for shorter and longer distances. It appears that the logarithm of distance decay can be described adequately as a (downward) logistic function of log cost.
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