10. What was the major sign that lead Professor Shiller to predict the crash of the housing market?

• Housing prices had been rising for 100 years, but then suddenly started to fall.
• Housing prices had been rising at a steady rate for 100 years, but then suddenly started to rise at a much higher rate.
• Housing prices had been falling for 100 years, but then suddenly started to rise.
• Housing prices had been relatively constant for 100 years, but then suddenly started to rise.