Supply-Side Economics
by James D. Gwartney,
professor of economics and director of the Gus A. Stavros Center for the Advancement of Free Enterprise and Economic Education at Florida State University. He was previously chief economist of the Joint Economic Committee of the U.S. Congress.
The term âsupply-side economicsâ is used in two different but related ways. Some use the term to refer to the fact that production (supply) underlies consumption and living standards. In the long run, our income levels reflect our ability to produce goods and services that people value. Higher income levels and living standards cannot be achieved without expansion in output. Virtually all economists accept this proposition and therefore are âsupply siders.â
âSupply-side economicsâ is also used to describe how changes in marginal tax rates influence economic activity. Supply-side economists believe that high marginal tax rates strongly discourage income, output, and the efficiency of resource use. In recent years, this latter use of the term has become the more common of the two and is thus the focus of this article.
The marginal tax rate is crucial because it affects the incentive to earn. The marginal tax rate reveals how much of oneâs additional income must be turned over to the tax collector as well as how much is retained by the individual. For example, when the marginal rate is 40 percent, forty of every one hundred dollars of additional earnings must be paid in taxes, and the individual is permitted to keep only sixty dollars of his or her additional income. As marginal tax rates increase, people get to keep less of what they earn.
An increase in marginal tax rates adversely affects the output of an economy in two ways. First, the higher marginal rates reduce the payoff people derive from work and from other taxable productive activities. When people are prohibited from reaping much of what they sow, they will sow more sparingly. Thus, when marginal tax rates rise, some peopleâthose with working spouses, for exampleâwill opt out of the labor force. Others will decide to take more vacation time, retire earlier, or forgo overtime opportunities. Still others will decide to forgo promising but risky business opportunities. In some cases, high tax rates will even drive highly productive citizens to other countries where taxes are lower. These adjustments and others like them will shrink the effective supply of resources, and therefore will shrink output.
Second, high marginal tax rates encourage tax-shelter investments and other forms of tax avoidance. This is inefficient. If, for example, a one-dollar item is tax deductible and the individual has a marginal tax of 40 percent, he will buy the item if it is worth more than sixty cents to him because the true cost to him is only sixty cents. Yet the one-dollar price reflects the value of resources given up to produce the item. High marginal tax rates, therefore, cause an item with a cost of one dollar to be used by someone who values it less than one dollar. Taxpayers facing high marginal tax rates will spend on pleasurable, tax-deductible items such as plush offices, professional conferences held in favorite vacation spots, and various fringe benefits (e.g., a company luxury automobile, business entertainment, and a company retirement plan). Real output is less than its potential because resources are wasted producing goods that are valued less than their cost of production.
Critics of supply-side economics point out that most estimates of the elasticity of labor supply indicate that a 10 percent change in after-tax wages increases the quantity of labor supplied by only 1 or 2 percent. This suggests that changes in tax rates would exert only a small effect on labor inputs. However, these estimates are of short-run adjustments. One way to check the long-run elasticity of labor supply is to compare countries, such as France, that have had high marginal tax rates on even middle-income people for a long time with countries, such as the United States, where the marginal rates have been persistently lower. Recent work by edward prescott, corecipient of the 2004 Nobel Prize in economics, used differences in marginal tax rates between France and the United States to make such a comparison. Prescott found that the elasticity of the long-run labor supply was substantially greater than in the short-run supply and that differences in tax rates between France and the United States explained nearly all of the 30 percent shortfall of labor inputs in France compared with the United States. He concluded:
I find it remarkable that virtually all of the large difference in labor supply between France and the United States is due to differences in tax systems. I expected institutional constraints on the operation of labor markets and the nature of the unemployment benefit system to be more important. I was surprised that the welfare gain from reducing the intratemporal tax wedge is so large. (Prescott 2002, p. 9)
The supply-side economic policy of cutting high marginal tax rates, therefore, should be viewed as a long-run strategy to enhance growth rather than a short-run tool to end recession. Changing market incentives to increase the amount of labor supplied or to move resources out of tax-motivated investments and into higher-yield activities takes time. The full positive effects of lower marginal tax rates are not observed until labor and capital markets have time to adjust fully to the new incentive structure.
Because marginal tax rates affect real output, they also affect government revenue. An increase in marginal tax rates shrinks the tax base, both by discouraging work effort and by encouraging tax avoidance and even tax evasion. This shrinkage necessarily means that an increase in tax rates leads to a less than proportional increase in tax revenues. Indeed, economist Arthur Laffer (of âLaffer curveâ fame) popularized the notion that higher tax rates may actually cause the tax base to shrink so much that tax revenues will decline, and that a cut in tax rates may increase the tax base so much that tax revenues increase.
How likely is this inverse relationship between tax rates and tax revenues? It is more likely in the long run when people have had a long time to adjust. It is also more likely when marginal tax rates are high, but less likely when rates are low. Imagine a taxpayer in a 75 percent tax bracket who earns $300,000 a year. Assume for simplicity that the 75 percent tax rate applies to all his income. Then the government collects $225,000 in tax revenue from this person. Now the government cuts tax rates by one-third, from 75 percent to 50 percent. After the tax cut, this taxpayer gets to keep $50, rather than $25, of every $100, a 100 percent increase in the incentive to earn. If this doubling of the incentive to earn causes him to earn 50 percent more, or $450,000, then the government will get the same revenue as before. If it causes him to earn more than $450,000, the government gets more revenue.
Now consider a taxpayer paying a tax rate of 15 percent on all his income. The same 33 percent rate reduction cuts his rate from 15 percent to 10 percent. Here, take-home pay per $100 of additional earnings will rise from $85 to $90, only a 5.9 percent increase in the incentive to earn. Because cutting the 15 percent rate to 10 percent exerts only a small effect on the incentive to earn, the rate reduction has little impact on the amount earned. Therefore, in contrast with the revenue effects in high tax brackets, tax revenue will decline by almost the same percentage as tax rates in the lowest tax brackets. The bottom line is that cutting all rates by a third will lead to small revenue losses (or even revenue gains) in high tax brackets and large revenue losses in the lowest brackets. As a result, the share of the income tax paid by high-income taxpayers will rise.
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