Economists from the University of Tennessee concluded that while there would be many desirable macroeconomic effects, adoption of a national retail sales tax would also have serious effects on state and local government finances. Economist Bruce Bartlett stated that if the states did not conform to the FairTax, they would have massive confusion and complication as to what is taxed by the state and what is taxed by the federal government. In addition, sales taxes have long exempted all but a few services because of the enormous difficulty in taxing intangibles—Bartlett suggests that the state may not have sufficient incentive to enforce the tax. University of Michigan economist Joel Slemrod argues that states would face significant issues in enforcing the tax. "Even at an average rate of around five percent, state sales taxes are difficult to administer." University of Virginia School of Law professor George Yin states that the FairTax could have evasion issues with export and import transactions. The President's Advisory Panel for Federal Tax Reform reported that if the federal government were to cease taxing income, states might choose to shift their revenue-raising to income. Absent the Internal Revenue Service, it would be more difficult for the states to maintain viable income tax systems.