Christopher Sims, 68, a professor at Princeton University, looks as a passerby congratulates him for winning the Nobel Prize in economics, Monday, Oct. 10, 2011, in Princeton, N.J. Sims won the Nobel economics prize on Monday for research that sheds light on the cause-and-effect relationship between the economy and policy instruments such as interest rates and government spending. Thomas Sargent, also a professor at Princeton, was also awarded the honor. (AP Photo/Julio Cortez)