  We study the global dynamics of the universe within the framework of the
Interacting Dark Matter (IDM) scenario. Assuming that the dark matter obeys the
collisional Boltzmann equation, we can derive analytical solutions of the
global density evolution, which can accommodate an accelerated expansion,
equivalent to either the {\em quintessence} or the standard $\Lambda$ models,
with the present time located after the inflection point. This is possible if
there is a disequilibrium between the DM particle creation and annihilation
processes with the former process dominating, which creates an effective source
term with negative pressure. Comparing the predicted Hubble expansion of one of
the IDM models (the simplest) with observational data we find that the
effective annihilation term is quite small, as suggested by a variety of other
recent experiments.
