Tobin’s q und private Investitionsausgaben. Einige analytische Aspekte und empirische Ergebnisse

The article deals with some aspects of private investment decisions. Using model computations it is demonstrated that neither nominal nor real interest rates on financial assets can determine the investment calculus to a major part. Then Tobin's q-concept is introduced. Some empirical results on measuring the real rate of return and the cost of capital and thus Tobin's q for Germany are reported. In contrary to some other investigations the empirically measured q is always greater than unity. An analytical decomposition of q shows that this must be the case in a growing economy. A simple graphical exposition is suggested to demonstrate why only under unlikely assumptions q can drop below unity. This exposition also offers a rough explanation of the empirically observed variations of q