Cullen Roche – in response to Paul Krugman – says Keynesians should learn to love tax cuts. His argument is that since Keynesians believe in the principle of effective demand and that since tax rate cuts boosts domestic demand and hence output, it is surprising to find Paul Krugman not favouring tax cuts.

Tax cuts raise output by increasing disposable incomes of economic units who will raise their expenditures in response. This via a multiplier effect will raise output. But it’s not as if tax rate cuts is the only tool available to the government.

Let’s see 4 different ways the government can boost domestic demand:

1. Raise government expenditures,
2. Decrease tax rates,
3. Raise government expenditures and decrease tax rates, and,
4. Increase government expenditures and raise tax rates.

The expansionary nature of the first three ways above is obvious. For the fourth, it depends on the numbers. So if the government raises tax rates from say 25% to 30% and increases government expenditure by 1%, it is likely contractionary. Instead, if the government increases its expenditure by 25%, it is expansionary.

These are not the only ways available for demand management. The government by coordinating with  the central bank can reduce interest rates. It can make lending/borrowing easier by other ways. It can give guarantees to bonds issued by corporations, thus giving an incentive for corporations to increase expenditures. It can raise tariffs on imports. There are several ways but here those things are less relevant for now.

Each of the four ways above has a different effect on output and the distribution of income. Tax cuts usually favour economic units who earn more. Richer economic units such as rich households have a lower propensity to consume and hence this will have a smaller multiplier effect. If Keynesians favour tax cuts, they’d favour it for low earning households than for corporations.

Of course, the multiplier effect is not a complete argument in itself as the opponents might argue “So cut taxes even more according to your logic”. But at any rate, let’s see how it works.

In stock-flow-consistent models, there’s the concept of a fiscal stance toward which GDP converges for a given government expenditure G and a tax rate θ. So we have

GDP = G/θ

With that,

dGDP/GDP = dG/G − dθ/θ

So a percentage rise in government expenditure will have the same multiplier effect as a percentage fall in tax rate.

This of course is the long-run output. For the short run, the expression in the simplest Keynesian model:

GDP = G/(1 − α₁·(1 − θ))

α₁ < 1

The parameter α₁ is the propensity to consume.

In this case, i.e., for the short run,

dGDP/GDP = dG/G − [α₁·θ/(1 − α₁·(1 − θ))²]·dθ/θ

By taking some values such as 0.6 for α₁ and 25% for θ, you can convince yourself that a proportional rise in government expenditure is more effective than a proportional fall in tax rates. Of course, this is not a complete argument but illustrative. If a tax rate cut of x% doesn’t achieve a $1 rise in government expenditure, one can make the case for a higher tax rate cut to achieve a similar result.

Apart from that there are other implicit assumptions of the model: there is no income inequality in the simplest Keynesian models. So rich economic units will have a lower propensity to spend: households working as employees of firms with higher compensation will have lower propensity to consume. Households may have an even lesser propensity to consume out of other incomes such as interest and dividends.

So the multiplier analysis illustrates that a tax cut for richer economic units is not the same as the poorer units because the multiplier in the short run depends on the propensities to spend.

The correct stand hence is about the distributional effects of fiscal policy and the effect on output. So the correct stand is to argue for a rise in government expenditure and fair rates of taxes for economic units. Many economic units will have to pay higher taxes in this view. What’s fair of course is debatable but at least in this line of argument, souls believing in the principle of effective demand needn’t love “tax cuts”.

There is another argument for not promoting lower tax rates. This is because once tax rates are reduced, it is politically difficult to raise it if needed.