Summary: The Summer Olympics (0.49%) have nearly double the percentage of reported doping cases as the Winter Olympics (0.28%). Athens 2004 was the most doped Olympics with 26 reported violations of anti-doping rules. Weightlifting is the most doped sport with 36 violations - 28.4% of all Olympic doping cases. Austria has the most doping violations in the Olympics (10) followed by Greece and Russia (tied for second with nine) and then the USA with eight. The four Olympic doping charts below were compiled from over 20 sources and provide a handy summary of doping in the Olympic Games from 1968-2010.
The number of doping cases reported refers to the number of positive tests found by the International Olympic Committee and the WADA-accredited laboratory run by anti-doping scientists from multiple countries. Athletes who tested positive for banned substances prior to the Olympics and were not allowed to compete are not included in these numbers. For example, WADA President John Fahey announced that at least 107 athletes who play Summer Olympic sports were sanctioned for doping in the six months leading up to the London Olympics, making them ineligible to compete.
*The 20 positive results include 14 people and six horse-doping cases.
**The IOC's report states that "the cases recorded covered not only adverse analytical findings reported by the laboratory, but also violations of the anti-doping rules, such as non-arrival within the set deadline for the test, providing a urine sample that did not conform to the established procedures, and refusal to comply with the procedures or to deliver urine."
***The World Anti-Doping Agency's publication "Report of the Independent Observers: XXI Olympic Winter Games, Vancouver 2010" states that the IOC collected 36 additional blood samples for Athlete Biological Passports, which are "based on the monitoring of an athlete's biological variables over time to facilitate indirect detection of doping on a longitudinal basis, rather than on the traditional direct detection of doping." These data are not included in the table.
Tables III and IV: The data for the number of doping cases reported by sport and the number of doping cases reported by country were extracted from multiple athlete pages on Sports-Reference.com (accessed Sep. 16, 2011) and a 2003 paper written by Honorable Justice J. EJ. Spender, Judge of the Federal Court of Australia and Member of the Court of Arbitration for Sport, titled "The Integrity of Sporting Performance at the Olympic Games and at Other Elite Sports Events," (270 KB) and delivered at the 9th Greek Australian Legal and Medical Conference in Greece, in addition to the citations below.