1# huiaii
From wiki
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Relative risk aversionThe
Arrow-Pratt measure of relative risk-aversion (RRA) or
coefficient of relative risk aversion is defined as

.
Like for absolute risk aversion, the corresponding terms
constant relative risk aversion (CRRA) and
decreasing/increasing relative risk aversion(DRRA/IRRA) are used. This measure has the advantage that it is still avalid measure of risk aversion, even if it changes from risk-averse torisk-loving, i.e. is not strictly convex/concave over all
c.A constant RRA implies a decreasing ARA, but the reverse is not alwaystrue. However, as a specific example, the expected utility function
u(
c) = log(
c) does imply RRA = 1.
In
intertemporal choice problems, the
elasticity of intertemporal substitution is often unable to be disentangled from the coefficient of relative risk aversion. The
isoelastic utility function
exhibits constant relative risk aversion with
Ru(
c) = ρ and the elasticity of intertemporal substitution

. When ρ = 1 and one is subtracted in the numerator (facilitating the use of
l'Hôpital's rule), this simplifies to the case of
log utility, and the
income effect and
substitution effect on saving exactly offset.