One can argue what is or it isn't the optimal corporate tax rate, but the problem is this, we live in a globalized economy so we make our corporate tax rates uncompetitive companies will just pack up and move elsewhere.  Part of the reason the US has so much outsourcing is their high corporate tax rate.  Part of the reason Ireland became the Celtic tiger was their low corporate tax rate.  More importantly when corporate taxes are raised, corporations rarely eat the cost, they just pass it onto the consumers in higher prices.