Of course it is easier to fake age in countries such as Kenya and Ethiopia but don't you think if it was widespread, then the seniors could not reproduce the results of the junior level at world stage? That is certainly not the case for countries like Kenya and Ethiopia; seniors dominate the same race events as the juniors do!
I find it fascinating that the argument goes this way: "they defeat us at youth championships because they are over-age but they defeat us at other stages because they are doped."
On related note I am curious about the benefits of age-cheating for the individual because I don't believe there is much monetary incentive at this competition level, no? The fact that an athlete would do this means they are not that great and can't keep up with their peers in international stage, which means little chance for any senior career. For instance, Kipketer in this race is never going to make any Kenyan team for 800M if he is already over 20 and with a PB of 1:48 - several Kenyans can do this easily.