Tyler Cowen tells us in this Bloomberg piece that the Republicans are right to say that their plans for a big cut in the corporate tax will boost investment. (He is still opposed to the overall package.) I've had several people ask me about this one. I'll give the usual economists' answer: it depends.
If the argument is that other things equal, more cash in corporate coffers means more investment, I'm with Tyler. If we throw a huge pile of money at corporate America, at least some of it has to end up being invested, so Tyler is right on this point.
On the other hand should we expect the investment boom projected by the White House and Tax Foundation, where the capital stock will be 30 percent higher in ten years as a result of the tax cut? That one seems pretty nutty. (Tyler doesn't endorse this view.) There are and have been large disparities in after-tax rates of return between countries. The argument for an investment boom depends on an equalization in after-tax rates of return across countries. (I know, we can wave our hands and explain that by risk premia, but that is just hand waving.) There is little reason to believe that a change in the corporate income tax rate will have a huge effect on investment, even if we can say the direction is to raise it.
It is also worth asking about the other things equal assumption. Suppose that the Fed sees higher projected deficits and decides it has to raise interest rates faster and further. It is entirely possible that these interest rate hikes more than offset any positive effect that the tax cuts have on investment, resulting in a net negative.
Another possibility is that the larger deficits embolden the deficit hawks who then take the hatchet to transfer programs like Social Security, Medicare, and food stamps. The vast majority of this money is spent quickly by the people who get it. The reduction in demand from cuts to these programs could lead to a fall in demand in the economy, thereby reducing the incentive for firms to invest.
We can also envision a story in which state governments are forced to reduce taxes, since their residents can no longer deduct state and local taxes from their federal income taxes. This could lead to a reduction in spending on infrastructure and education, which could also have a negative effect on private investment.
In addition, taxing tuition waivers for grad schools could drastically reduce the supply of new graduates in computer sciences, biotech, and other areas requiring highly skilled workers. This could also lead to less investment.
In all of these cases, the net effect of the Republican tax package could be to reduce investment, but Tyler is right that the immediate effect of a cut in corporate taxes should be to raise investment.