Corporate finance side of the Q theory of investment

This paper presents a model of a firm under uncertainty in which the financial and investment decisions are simultaneously determined. If profits are small relative to investment, the firm finances a constant fraction of incremental investment by debt and the rest by retentions. If profits are large relative to investment, a constant fraction of marginal finance comes from debt and the rest from new shares. In these two financing regimes a one-to-one relationship between optimal investment and Q can be derived. No such relation exists in the third and intermediate regime in which incremental investment is entirely debt-financed.