The Revenue Limits of Tax and Spend - Whether rates are high or low, evidence shows our tax system won't collect more than 20% of GDP

The Revenue Limits of Tax and Spend. By DAVID RANSON
Whether rates are high or low, evidence shows our tax system won't collect more than 20% of GDP.
WSJ, May 17, 2010

The Greeks have always been trendsetters for the West. Washington has repudiated two centuries of U.S. fiscal prudence as prescribed by the Founding Fathers in favor of the modern Greek model of debt, dependency, devaluation and default. Prospects for restraining runaway U.S. debt are even poorer than they appear.

U.S. fiscal policy has been going in the wrong direction for a very long time. But this year the U.S. government declined to lay out any plan to balance its budget ever again. Based on President Obama's fiscal 2011 budget, the Congressional Budget Office (CBO) estimates a deficit that starts at 10.3% of GDP in 2010. It is projected to narrow as the economy recovers but will still be 5.6% in 2020. As a result the net national debt (debt held by the public) will more than double to 90% by 2020 from 40% in 2008. The current Greek deficit is now thought to be 13.6% of a far smaller GDP. Unlike ours, the Greek insolvency is not too large for an international rescue.

As sobering as the U.S. debt estimates are, they are incomplete and optimistic. They do not include deficit spending resulting from the new health-insurance legislation. The revenue numbers rely on increased tax rates beginning next year resulting from the scheduled expiration of the Bush tax cuts. And, as usual, they ignore the unfunded liabilities of social insurance programs, even though these benefits are officially recognized as "mandatory spending" when the time comes to pay them out.

The feds assume a relationship between the economy and tax revenue that is divorced from reality. Six decades of history have established one far-reaching fact that needs to be built into fiscal calculations: Increases in federal tax rates, particularly if targeted at the higher brackets, produce no additional revenue. For politicians this is truly an inconvenient truth.

[Hauser's Law http://sg.wsj.net/public/resources/images/ED-AL524A_ranso_NS_20100516181943.gif]

The nearby chart shows how tax revenue has grown over the past eight decades along with the size of the economy. It illustrates the empirical relationship first introduced on this page 20 years ago by the Hoover Institution's W. Kurt Hauser—a close proportionality between revenue and GDP since World War II, despite big changes in marginal tax rates in both directions. "Hauser's Law," as I call this formula, reveals a kind of capacity ceiling for federal tax receipts at about 19% of GDP.

What's the origin of this limit beyond which it is impossible to extract any more revenue from tax payers? The tax base is not something that the government can kick around at will. It represents a living economic system that makes its own collective choices. In a tax code of 70,000 pages there are innumerable ways for high-income earners to seek out and use ambiguities and loopholes. The more they are incentivized to make an effort to game the system, the less the federal government will get to collect. That would explain why, as Mr. Hauser has shown, conventional methods of forecasting tax receipts from increases in future tax rates are prone to over-predict revenue.

For budget planning it's wiser and safer to assume that tax receipts will remain at a historically realistic ratio to GDP no matter how tax rates are manipulated. That leads me to conclude that current projections of federal revenue are, once again, unrealistically high.

Like other empirical "laws," Hauser's Law predicts within a range of approximation. Changes in marginal tax rates do not make a perceptible difference to the ratio of revenue to GDP, but recessions do. When GDP falls relative to its potential, tax revenue falls even more. History shows that, in an economy with no "output gap" between GDP and potential GDP, a ratio of federal revenue to GDP of no more than 18.3% would be realistic.

In this form, Hauser's Law provides a simple basis for testing the validity of any government's revenue projections. Today, since the economy already suffers from a large output gap that is expected to take many years to close, 18.3% must be a realistic upper limit on the ratio of budget revenues to GDP for years to come. Any major tax increase will reduce GDP and therefore revenues too.

But CBO projections based on the current budget show this ratio reaching 18.3% as early as 2013 and rising to 19.6% in 2020. Such numbers implicitly assume that the U.S. labor market will get back to sustainable "full employment" by 2013 and that GDP will exceed its potential thereafter. Not likely. When the projections are tempered by the constraints of Hauser's Law, it's clear that deficit spending will grow faster than the official estimates show.

Mr. Ranson is the head of research at H. C. Wainwright & Co. Economics.