Financial Frictions, Investment and Tobin's q

We develop a model of investment with financial constraints and use it to investigate the relation between investment and Tobin’s q. A firm is financed partly by insiders, who control its assets, and partly by outside investors. When insiders’ wealth is scarce, they earn a rate of return higher than the market rate of return, i.e. insiders earn a quasi-rent on invested capital. This rent is priced into the value of the firm, so Tobin’s q is driven by two forces: changes in the value of invested capital, and changes in the value of the insiders’ future rents. The second effect weakens the correlation between q and investment. We calibrate the model and show that, thanks to this effect, the model can generate realistic correlations between investment, q and cash flow