"There is always a disposition in people's minds to think that existing conditions will be permanent. When the market is down and dull, it is hard to make people believe that this is the prelude to a period of activity and advance. When prices are up and the country is prosperous, it is always said that while preceding booms have not lasted, there are circumstances connected with this one which makes it unlike its predecessors and gives assurance of permanency. The one fact pertaining to all conditions is that they change."

Charles Dow
Co-founder of Dow Jones & Company