From John Cochrane at The Grumpy Economist, The Buyback Fallacy:

Suppose company 1 gets a tax cut, doesn’t really know what to do with the money — on top of all the extra cash the company may already have — as it doesn’t have very good investment projects. It  sends the money to shareholders. Well, what do shareholders do with it? (Hint: track the money.) They most likely roll the money in to other investments. They find company 2 that does need the money for investment, and send it to that company. In the end, they only consume it if nobody has any good investment ideas.

If company 1 doesn’t have any good investment ideas, even after the tax cut, and company 2 does have some good investment ideas, made better after the tax cut, the economy needs to get money from company 1 to company 2. Company 1 could buy company 2; company 1 could invest in company 2 by buying its stock or buying its debt (all that “cash” you hear about); company 1 could return money to shareholders, and the shareholders could invest in company 2. They’re all the same, to economics. Of all the ways to do this, actually, the last might well be the most efficient. Shareholders might have better ideas about good investments than managers of a company that doesn’t have any good investment ideas.

The larger economic point: In the end, investment in the whole economy has nothing to do with the financial decisions of individual companies. Investment will increase if the marginal, after-tax, return to investment increases. Lowering the corporate tax rate operates on that marginal incentive to new investments. It does not operate by “giving companies cash” which they may use, individually, to buy new forklifts, or to send to investors. Thinking about the cash, and not the marginal incentive, is a central mistake. (It’s a mistake endemic to Keynesian economics, but the case here is supply-side, incentive oriented.)

The point is the same as one I made in an earlier post, not to expect “repatriation” of corporate profits to make much difference to investment. Apple Ireland could already put money in a bank that lends to a US bank that lends to Apple US, if that money’s best use was in the US. The marginal profitability of investment is all that matters.