Artificial trees became increasingly popular during the late 20th century. Users of artificial Christmas trees assert that they are more convenient, and, because they are reusable, much cheaper than their natural alternative. They are also considered much safer as natural trees can be a significant fire hazard. Between 2001 and 2007 artificial Christmas tree sales in the U.S. jumped from 7.3 million to 17.4 million. Currently it is estimated that around 58% of Christmas trees used in the United States are artificial while numbers in the United Kingdom are indicated to be around 66%.