create what we term ‘management factories’—bureaucracies to forecast, schedule, plan, manage inventories and set budgets and targets. This overhead is required because economies of scale are incompatible with ‘pull’. If a factory builds to order, it responds directly to demand. If it is not building to order, it must estimate demand and schedule production of the different batches so that they roughly match over time. In other words, the logic is ‘push’ as opposed to ‘pull’. Instead of making only the things that the customer wants to buy the factory must sell what it has made. If, as is usually the case, it gets its estimates wrong (after all, a basic model may have thousands of variants) it must either leave unwanted models to depreciate in inventory or organize promotions or other inducements for customers to buy what they didn’t originally chose. ‘Push’ is to guess what to make, make it, see if anyone wants it, and give someone something to buy it. ‘Pull’ is to sell it, make it and collect the money