Why must the rate of GDP growth be positive? There are always expectations that GDP should be growing at a certain rate. This is what I see in the newspapers. I am not an economics major and this is a very basic student question. After adjusting for level of prices, meaning that forget about inflation and price related issues, it is expected to grow at say $2\%$. Why is this a case and what should it be driven by? Assume there is an economy that only produces apples, for simplicity. So, it is expected to make $2\%$ more apples every year? So the growth would be driven by the larger amount of goods produced? Why is this economy expected to make more apples every year?
You would expect the rate of growth to be generally positive because inventing things or inventing more efficient ways of doing things, is generally a one way process - things don't get un-invented. So we would expect things that are made by machines to be made ever more quickly as the machines evolve and improve. Periods of negative growth are likely to correspond to some financial cock-up (e.g. asset bubbles) or increasing scarcity of some natural resources for which a replacement can not be found.