Great Britain consumes about 8 million trees annually, while in the United States between 35 and 40 million trees are sold during the Christmas season. Artificial Christmas trees are mostly produced in the Pearl River delta area of China. Christmas tree prices were described using a Hotelling-Faustmann model in 2001, the study showed that Christmas tree prices declined with age and demonstrated why more farmers do not price their trees by the foot. In 1993, economists made the first known demand elasticity estimates for the natural Christmas tree market.