Rekrunner, it surprises me to be corrected on the use of the expression "beg the question", because it is entirely appropriate to use that expression in respect of a claim that rests on an assumption. Yes - Kenya has a high number of elite runners, but some of them may well be elite by virtue of bring doped. That is a reasonable inference to draw when a country has an identified doping problem - as Kenya does. (And I am not saying Kenya is by any means unique in this, or is even necessarily the worst offender. It is not. It is everywhere now.)
I appreciate you and some others here are generally better informed than I am about the sport, as well as doping, and you are clearly more well-versed in statistics than I am. But this is not an issue than can be decided by statistics, or by a single definitive study of research. Doping is by its nature secretive. We are having to speculate not only about individuals (unless they test positive - which is rare) but about the true extent of the problem. The figures themselves are a kind of guesswork. We are looking for a smoking gun, and typically with a crime scene the evidence is varied and incomplete, and requires a judgment based on what is likely or probable, rather than what is known or certain.
But whether we think only a very small percentage of elite runners dope, or we think it is 90% of Olympians (as Victor Conte, formerly of Balco, claims), the problem is out there and all the indications are it is getting away from us.
My own view is that doping works, or athletes wouldn't choose to go down that path, and the authorities would not be concerned to stamp it out. It works for anybody, but not necessarily the same way or to the same extent. I also believe it works for altitude-trained athletes, such as Kenyans, or they wouldn't be using it in the apparent numbers they are. (More will be using it than those who are caught. And champions are being caught.)
Doping improves on what you start with. Jose Canseco, the American baseball player, said doping makes an average athlete good, a good athlete outstanding, and an outstanding athlete invincible. (He doped and admitted to it in his autobiography). If doping couldn't improve an altitude-trained athlete then we would say Kenya doesn't have a doping problem - because doping doesn't help altitude athletes, and Kenyans live at altitude. I don't know many outside these boards that would maintain that. Certainly not the Kenyan authorities, who now appear concerned with catching the cheats.
So where does that leave us? Well, currently all elite performances will continue to have a question-mark over them, when there is such a wide disparity between the numbers of dopers who are caught (very few) and those who aren't. Testing needs to improve, along with the willingness of sports governance bodies to enforce it. It doesn't help when the body responsible for leading anti-doping appears to have lost the confidence of athletes.