Tax revenues

Tax revenue is the income that is gained by governments through taxation.

Just as there are different types of tax, the form in which tax revenue is collected also differs; furthermore, the agency that collects the tax may not be part of central government, but may be a third party licensed to collect tax which they themselves will use. For example, in the UK, the Driver and Vehicle Licensing Agency (DVLA) collects vehicle excise duty, which is then passed onto HM Treasury.

Tax revenues on purchases come in two forms: "tax" itself is a percentage of the price added to the purchase (such as sales tax in U.S. states, or VAT in the UK), while "duties" are a fixed amount added to the purchase price (e.g., for cigarettes). In order to calculate the total tax raised from these sales, we must work out the effective tax rate multiplied by the quantity supplied.

The effect of a change in taxation level on total tax revenue depends on the good being investigated, and in particular on its price elasticity of demand. Where goods have a low elasticity of demand (they are price inelastic), an increase in tax or duty will lead to a small decrease in demand—not enough to offset the higher tax raised from each unit. Overall tax revenue will therefore rise. Conversely, for price-elastic goods, an increase in tax rate or duty would lead to a fall in tax revenue.

The Laffer curve theorises that, even for price-inelastic goods (such as addictive necessary items), there will be a tax revenue maximising point, beyond which total tax revenue will fall as taxes increase. This may be due to:

The Laffer curve, however, is not universally accepted; Paul Krugman referred to it as "junk economics".

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