Personal income taxes are levied on wage workers and the self-employed. Taxes on business profits are graduated. The top tax rate on personal and corporate income tax is 35%. Zakat (the religious charity tax) is state-enforced, but under the republican regime its estimation is a voluntary concern of each individual. Yemeni businessmen have been trying to abolish Zakat as an obligatory levy entirely, leaving it to the discretion of each individual to give to the needy. Taxes were increased substantially in the 1970s, with taxes on imports providing about 70% of total tax revenues. There are excise duties, road and vehicle taxes, port fees, a tax on rents, and telegraph fees. The state also derives income from the confiscated property of the imamate. The chronic budget deficits of the 1980s forced the government to place considerably more emphasis on the traditionally lax collection of taxes. In early 2002 a general sales tax (GST) was signed into law, but its implementation was delayed pending a review of the country's indirect tax system.