Former Senator Mike Gravel has called it a "green tax". The concepts of environmental economics come into play with some of the aspects suggested. With the FairTax being levied only on new goods and services, with no federal tax charged on used goods, supporters suggest a systemic incentive to buy used goods is introduced. Consequently, re-use and re-sale of used goods is encouraged. With the subsequent increase of the used-goods market (and with new goods being taxed) it is suspected that people would put more emphasis on maintenance of things for longer use and better resale value, and that they may also shy away from disposable goods. The significant reduction of paperwork for IRS compliance and tax forms is estimated to save about 300,000 trees each year. With the expected increase of business and manufacturing movement to the U.S., more goods consumed domestically will be produced domestically. This may reduce international shipping and consequent environmental impact, as well as production in countries with less stringent pollution controls. The federal income tax system provides tax advantages to state and local municipal bonds. Specifically, the interest paid on such securities is exempt from federal taxation. This tax discount allows state and local governments to issue debt at low yields, which reduces their interest costs. By eliminating income taxes, FairTax would remove the federal tax advantage of holding state and local bonds as all investments would become tax free. However, the Treasury department has called for the elimination of these special tax provisions under the current system in an effort to broaden the tax base and reduce corporate tax rates. State and local governments often exempt their own taxes when issuing bonds, so they could still contain some advantages. Issuers may have to offer higher interest rates to attract investors. Americans For Fair Taxation argue that, after the fair tax goes into effect, corporate bond rates would drop; that new tax free yields will roughly equal their previous after tax value under the income tax; and that state and municipal bond holders would not need to change their rates. The current system of taxation, in many cases, provides incentives for illegal immigrants and companies that employ them. It is estimated that approximately 5 million illegal immigrants are paid off the books ("under the table") in cash allowing employee and employer to avoid paying federal taxes estimated at $35 billion a year. Advocates also claim the FairTax would provide incentive for illegal immigrants to legalize as they would otherwise not receive the FairTax rebate. Proponents believe that the FairTax would have positive effects on civil liberties that are sometimes charged against the income tax system. Some of these include social inequality, economic inequality, financial privacy, self-incrimination, unreasonable search and seizure, burden of proof, and due process.