  Although standard economics textbooks are seldom interested in production
networks, modern economies are more and more based upon suppliers/customers
interactions. One can consider entire sectors of the economy as generalised
supply chains. We will take this view in the present paper and study under
which conditions local failures to produce or simply to deliver can result in
avalanches of shortage and bankruptcies across the network. We will show that a
large class of models exhibit scale free distributions of production and wealth
among firms and that metastable regions of high production are highly
localised.
