Government levy on persons, groups, or businesses. Taxes are a general obligation of taxpayers and are not paid in exchange for any specific benefit. They have existed since ancient timesproperty taxes and sales taxes were known in ancient Romebut tariffs were favoured over internal taxes as a source of revenue. In modern economies, there has been a trend away from tariffs in favour of internal taxes, which provide the majority of revenues. Taxes have three functions: to cover government spending, to promote stable economic growth, and to lessen inequalities in the distribution of income and wealth. They have also been used for nonfiscal reasons, such as to encourage or discourage certain activities (e.g., cigarette consumption). Taxes may be classified as direct or indirect. Direct taxes are those that the taxpayer cannot shift onto someone else; they are mainly taxes on persons and are based on an individual's ability to pay as measured by income or net wealth. Direct taxes include income taxes, taxes on net worth, death duties (i.e., inheritance and estate taxes), and gift taxes. Indirect taxes are those that can be shifted in whole or in part to someone other than the person legally responsible for payment. These include excise taxes, sales taxes, and value-added taxes. Taxes may also be classified according to the effect they have on the distribution of wealth. A proportional tax is one that imposes the same relative burden on all taxpayers, unlike progressive taxes and regressive taxes.