We present a method to compute the averaged motion of all the critical
points of the squared distance between a point on a Keplerian orbit of
a NEA and a point on the orbit of the Earth: in particular we compute
the averaged motion of the MOID.  This computation is done over time
scales for which the chaoticity of the asteroid orbits is negligible,
but crossings with the orbits of the planets are taken into account.

The averaged evolution of the asteroids is computed by a generalized
averaging principle, suitable for planet crossing orbits such as the
ones of the NEAs; the critical points of the squared orbital distance
are computed by some algebraic geometry techniques.