All of the developed economies of the world are based upon consumption. People have to buy products or use services continually or the system will collapse. There is one critical flaw in this system and that is we all live on a planet that has finite resources. That the world does not contain enough materials to support endless growth would seem obvious to most of us. But, the current system has been designed with the assumption that economies can continue to grow for ever. All nations economies and indeed the world economy must grow by at least a few percent each year to remain in a healthy state. A few percent seems quite reasonable at first glance but to a mathematician who understands how exponential growth works this amount of growth results in huge increases in the numbers even after a relatively modest amount of time.