  We classify the asymptotic densities of the $\Delta^0_2$ sets according to
their level in the Ershov hierarchy. In particular, it is shown that for $n
\geq 2$, a real $r \in [0,1]$ is the density of an $n$-c.e.\ set if and only if
it is a difference of left-$\Pi_2^0$ reals. Further, we show that the densities
of the $\omega$-c.e.\ sets coincide with the densities of the $\Delta^0_2$
sets, and there are $\omega$-c.e.\ sets whose density is not the density of an
$n$-c.e. set for any $n \in \omega$.
