Continuous approximations that are ordinary differential equations (ODEs) o
r stochastic differential equations (SDEs) are often used to study the prop
erties of discrete stochastic processes. We show that different ways of tak
ing the continuous limit of the same model may result in either an ODE or a
SDE and study the manner in which each approximates the discrete model. We
compare the asymptotic properties of the continuous equations with those o
f the discrete dynamics and show that they tend to provide a better approxi
mation when a gi ratel amount of variance of the discrete model is preserve
d in the continuous limit. Journal of Economic Literature Classification nu
mbers: C6, C7, D8. (C) 2000 Academic Press.