BERKELEY – At this stage in the worldwide fight against depression, it is useful to stop and consider just how conservative the policies implemented by the world’s central banks, treasuries, and government budget offices have been. Almost everything that they have done – spending increases, tax cuts, bank recapitalization, purchases of risky assets, open-market operations, and other money-supply expansions – has followed a policy path that is nearly 200 years old, dating back to the earliest days of the Industrial Revolution, and thus to the first stirrings of the business cycle.