You are a naive fool. Sorry not necessarily a personal attack, but it is the truth. Not 100% are doping - but much, much higher than most here would like to admit.
Take Kenyans for example - right now, people are dying in Kenya - people are getting hacked up left and right, houses are being burned to the ground, the government is believed to be corrupt by their own people - hence the violence, Athletics Kenya is universally known to be corrupt - yet for some asinine reason people think that their runners are above suspicion and would never touch drugs, yet "they" have no problem with hacking to death someone else - WTF is up with that?
How 'bout all of those Africans training and racing in the United States, are they part of any formal drug testing? Nope! Do you think that someone from Ethiopia or Kenya is going to fly to Albuquerque, NM to do some random drug tests on their athletes? Sorry, it ain't happening. The folks at NYC and other major marathons must be pressured into not handing out money to athletes who are not on a year round drug testing regimen.
Sorry, but EPO is out of your system within days of initially taking it - but the effects last for months. Unless someone is caught jabbing a syringe into their arms labeled "Illegal Performance Enhancing HGH" - it is undetectable - despite some of the pre-Olympic scare mongering.