The decreased economic well-being caused by the imposition of a tax. Taxing any product or activity makes it less attractive and gives people less incentive to purchase or undertake it. Taxpayers not only suffer from having less money because of the tax, they also suffer because the tax may change their behavior. Taxation results in deadweight loss which results in the economy functioning below optimal levels.

The market inefficiency that occurs when people change their behavior to avoid a tax creates a loss to society. A tax may cause individuals to buy less than they would prefer or to buy a different product or service than they really wanted. A tax can also cause workers to take additional leisure time rather than to work more when they know they will lose 35% of any additional dollar they earn to taxes. The higher the tax, the greater the welfare loss of taxation.