Why did God invent economists?

``Take the 2007-09 recession. It began in December 2007 and ended in June 2009. Markets act as a future discounting mechanism, often leading the economic data. The Standard & Poor's 500-stock index peaked in mid-October two months before the recession formally began. By the time the NBER, the group that formally dates these things, made its official announcement in December 2008, markets had fallen more than 30 percent. For investors, waiting for the official announcement was of little use.''