A 1999 study found that doctors treat black and white patients differently, even when their medical files are statistically identical. When they were shown patient histories and asked to make judgments about heart disease, the doctors were much less likely to recommend cardiac catheterization (a helpful procedure) to black patients. A 2015 study found that pediatricians were more likely to undertreat appendicitis pain in black children than white children. A 2017 study found that medical staff which was treating anterior cruciate ligament (ACL) injuries perceived black collegiate athletes as having higher pain tolerance than white athletes. A study by University of Toronto and Ohio State University economists found substantial evidence of racial discrimination against black veterans in terms of medical treatment and awarding of disability pensions in the late 19th and early 20th century; the discrimination was substantial enough to account for nearly the entire black-white mortality gap in the period. A 2019 study in "Science" found that one widely used algorithm to assess health risks falsely concluded that "Black patients are healthier than equally sick White patients", thus leading health care providers to provide lower levels of care for black patients.