In the late 20th century and early 21st century the vulture population on the Indian subcontinent declined (see Indian vulture crisis) by over 97% as of 2008, primarily due to diclofenac poisoning of the birds following the introduction of that drug for livestock in the 1990s, until banned for cattle by the Indian government in 2006. The few surviving birds are often unable to fully consume the bodies. In 2001, Parsi communities in India were evaluating captive breeding of vultures and the use of "solar concentrators" (which are essentially large mirrors) to accelerate decomposition. Some have been forced to resort to burial, as the solar collectors work only in clear weather. Vultures used to dispose of a body in minutes, and no other method has proved fully effective.