This is one of the best papers I have read in the last few years. Neat stuff!
Introduced in its contemporary form in 1946, but with roots that go back to the eighteenth century, the gravity law is the prevailing framework with which to predict population movement, cargo shipping volume and inter-city phone calls, as well as bilateral trade flows between nations. Despite its widespread use, it relies on adjustable parameters that vary from region to region and suffers from known analytic inconsistencies. Here we introduce a stochastic process capturing local mobility decisions that helps us analytically derive commuting and mobility fluxes that require as input only information on the population distribution. The resulting radiation model predicts mobility patterns in good agreement with mobility and transport patterns observed in a wide range of phenomena, from long-term migration patterns to communication volume between different regions. Given its parameter-free nature, the model can be applied in areas where we lack previous mobility measurements, significantly improving the predictive accuracy of most of the phenomena affected by mobility and transport processes.
ps. I've postponed this post for far too long because I was planning to start a study with some testing on the radiation model using Brazilian data (commuting, migration, national flights). However, I might face some (good!) turbulence in my professional/academic life in the next few months and I don't know when I'll get time for that.
Commuting landscapes (Fig 4)
[Image Source: Simini et al, 2011]