where the returning aircraft were unscathed, inferring that planes hit in those areas were the ones most likely to be lost. His work is considered seminal in the then-nascent discipline of operational research. Cats In a study performed in 1987, it was reported that cats who fall from less than six stories, and are still alive, have greater injuries than cats who fall from higher than six stories. It has been proposed that this might happen because cats reach terminal velocity after righting themselves at about five stories, and after this point they relax, leading to less severe injuries in cats who have fallen from six or more stories. In 1996, The Straight Dope newspaper column proposed that another possible explanation for this phenomenon would be survivorship bias. Cats that die in falls are less likely to be brought to a veterinarian than injured cats, and thus many of the cats killed in falls from higher buildings are not reported in studies of the subject. Tropical trees Tropical vines and lianas are often viewed as macro-parasites of trees that reduce host tree survival. The proportion of trees infested with lianas was observed to be much greater in shade-tolerant, heavy wooded, slow-growing tree species while light-demanding, lighter wooded and fast-growing species are often liana free. Such observations led to the expectation that lianas have stronger negative effects on shade-tolerant species. Further investigations, however, revealed that liana infestation is far more harmful to light-demanding fast-growing tree species where liana infestation greatly decreases survival such that the observable sample is biased towards those that survived and are liana-free. Hence, the observable sample of trees with lianas in their crown is skewed due to survivorship bias. Studies of evolution Large groups of organisms called clades that survive a long time are subject to various survivorship biases such as the "push of the past", generating the illusion that clades in general tend to originate with a high rate of diversification that then slows through time. Portrayal of disability Certain portrayals of disability, such as inspiration porn (where disabled people are able to do ordinary things) and supercrip stereotype (where disabled people do extraordinary things) could be inferred to mean barriers don't exist or that there are no special needs. Many disabled people remain unemployed or unsupported. Employment discrimination is reported to play a significant part in the high rate of unemployment among those with a