This paper studies optimal labor-income taxation in a simple model with credit constraints on firms. The labor-income tax rate and the shadow value on the credit constraint induce a wedge between the marginal product of labor and the marginal rate of substitution between labor and consumption. It is found that optimal policy prescribes a volatile path for the labor-income tax rate even in the presence of state-contingent debt and capital. In this respect, credit frictions are akin to a form of market incompleteness. Credit frictions break the equivalence between tax smoothing and wedge smoothing; therefore, as the tightness of the credit constraint varies over the business cycle, tax volatility is needed in order to counter this variation and, as a result, allow for wedge smoothing.

It is commonly accepted that credit market frictions are an important source of macroeconomic fluctuations. But what is the link between the two? And what is the driving factor of asset prices volatility? To answer these questions, we have introduced a specific credit friction, limited commitment, in a general equilibrium model with production and investment in productive capital, where agents can trade bonds. The model always displays a stationary equilibrium where bonds are traded. More importantly, limited commitment may generate stochastic endogenous fluctuations driven by self-fulfilling volatile expectations (sunspots), yielding credit and investment cycles and bond price volatility consistent with data.

This paper examines the behavior of the finance premium after technology and monetary shocks in a dynamic stochastic general equilibrium (DSGE) model where borrowers use a fraction of their production (output) as collateral. We show that this simple framework is capable of producing a countercyclical finance premium, while matching the well-documented stylized facts of macro dynamics. A key feature is the endogenous derivation of the default probability from break-even conditions, which results in the loan rate being set as a countercyclical finance premium over the cost of borrowing from the central bank. The latter is shown to provide an accelerator effect through which shocks can amplify the loan spread and the dynamic response of macro variables.