The Data of macroeconomics It is a capital mistake to theorize before one has data Insensibly one begins to twist facts to suit theories, instead of theories to fit facts. Sherlock holmes Scientists, economists, and detectives have much in common: they all want to figure out what's going on in the world around them. To do this, they rely on both theory and observation. They build theories in an attempt to make sense of what they see happening. They then turn to more systematic observation to eval- uate the theories validity. Only when theory and evidence come into line do they feel they understand the situation
