Demerit good
（重定向自Demerit goods）
In economics, a demerit good is a good or service whose consumption is considered unhealthy, degrading, or otherwise socially undesirable due to the perceived negative effects on the consumers themselves. It is over-consumed if left to market forces. Examples of demerit goods include tobacco, alcoholic beverages, recreational drugs, gambling, junk food and prostitution. Because of the nature of these goods, governments often levy taxes on these goods (specifically, sin taxes), in some cases regulating or banning consumption or advertisement of these goods.