Why is the shape of the Laffer curve for consumption tax different from that for labor income tax?

It is well known that the equivalence between consumption and labor income taxes holds. However, recent macroeconomic studies on the Laffer curves (tax revenue curves) that use dynamic general equilibrium models find that the Laffer curve for consumption tax might not be hump-shaped, but monotonically increas-ing, whereas that for labor income tax is hump-shaped. This study investigates the cause of the difference in the shapes of the two Laffer curves by decomposing the effects of an increase in a tax rate on the tax base into two parts: (i) the effects on the relative price of leisure (RPL), and (ii) the substitution and income effects. It is shown that the first effect with respect to the consumption tax rate is completely different from that with respect to the labor income tax rate; meanwhile, the second effect is common among the taxes and depends on the functional form of the util-ity. The elasticity of the RPL from an increasing consumption tax rate is at most 1, whereas it can be infinity in the case of labor income tax.