  We introduce economic models based on Boolean Delay Equations: this formalism
makes easier to take into account the complexity of the interactions between
firms and is particularly appropriate for studying the propagation of an
initial damage due to a catastrophe. Here we concentrate on simple cases, which
allow to understand the effects of multiple concurrent production paths as well
as the presence of stochasticity in the path time lengths or in the network
structure.
  In absence of flexibility, the shortening of production of a single firm in
an isolated network with multiple connections usually ends up by attaining a
finite fraction of the firms or the whole economy, whereas the interactions
with the outside allow a partial recovering of the activity, giving rise to
periodic solutions with waves of damage which propagate across the structure.
The damage propagation speed is strongly dependent upon the topology. The
existence of multiple concurrent production paths does not necessarily imply a
slowing down of the propagation, which can be as fast as the shortest path.
