The Q ratio of James Tobin is the ratio between the total value of stocks and the total value of underlying assets such as plants, inventory and equipment.
When this ratio goes above 1, stocks are overvalued. A rising ratio indicates that money isn’t going into developing plant and equipment. Instead we have an engineered equity bubble forming.
For more info, go to this Zerohedge article.
As of 2015, we are clearly overvalued and a correction will be a matter of time.
Correlation Economics (Backup) 