The Harberger triangle measures the welfare loss in the introduction of a new consumption tax. It was named after its inventor Arnold Harberger.
Given the market equilibrium ( Marshallian demand function ) without control (intersection of supply and demand ), a tax is introduced. Thus, the price to be paid by the consumer of on increases while the proceeds of the producer goes back on. With the increased price at the same time is the demand for the original market equilibrium on back. In addition to the tax revenue, consumer surplus and producer surplus shows the ( highlighted in red ) Harbergerdreieck the welfare loss ( additional load) the tax on.
The wider the base, the lower the additional load for the individual, because then the tax rate must not be so greatly increased in order to achieve a certain level of revenue.
The additional load equivalent to a welfare loss, made up of reductions in producer surplus and consumer surplus. Depending on the supply or demand respond as elastic on the tax bears principle of the higher proportion of the additional load that responds less elastic to the tax. The additional load increases almost exponentially with the tax increase. Therefore, it is advantageous to take a particularly broad mass of taxpayers with a low tax rate.