Tibetan exiles generally say that the number that have died in the Great Leap Forward, violence, or other unnatural causes since 1950 is approximately 1.2 million. However, this number is controversial. According to Patrick French, a supporter of the Tibetan cause who was able to view the data and calculations, the estimate is not reliable because the Tibetans were not able to process the data well enough to produce a credible total, with many persons double or triple counted. There were, however, many casualties, perhaps as many as 400,000. This figure is extrapolated from a calculation Warren W. Smith made from census reports of Tibet which show 200,000 "missing" from Tibet. Even anti-Communist resources such as "the Black Book of Communism" expresses doubt at the 1.2 million figure, but does note that according to the Chinese census, the total population of ethnic Tibetans in the PRC was 2.8 million in 1953, but only 2.5 million in 1964. It puts forward a figure of 800,000 deaths and alleges that as many as 10% of Tibetans were interned, with few survivors. Chinese demographers have estimated that 90,000 of the 300,000 "missing" Tibetans fled the region.