As I mentioned a moment ago, there are always economic and demographic shocks that affect the trajectories of individual family fortunes. With the aid of a fairly simple mathematical model, one can show that for a given structure of shocks of this kind, the distribution of wealth tends toward a long-run equilibrium and that the equilibrium level of inequality is an increasing function of the gap r − g between the rate of return on capital and the growth rate. Intuitively, the difference r − g measures the rate at which capital income diverges from average income if none of it is consumed and
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