Municipal solid waste management remains a challenge for highly urbanized societies. Due to a dense population and limited spaces for waste disposal, Taipei City's local government has implemented several policies for waste management since the 1980s.  One remarkable policy is a waste charging system named “Per-Bag Trash Collection Fee Program”, introduced in 2000, whereby residents are required to purchase specially designated garbage bags for waste disposal. Since its introduction, waste production has reduced by one-third and the collection of recyclable materials increased significantly.