Lake Palmer aka Monk wrote:
How do you know its harder to cheat and not get caught ?

You don't. So you cannot say you are certain its cleaner. Its probably eaiser to cheat and not get caught.
It's harder to get caught because screening is done at any time, in or out of season, randomly without warning.

In the past, competitors could use drugs to aid training, then give them up before an event to let them pass from the system.

It certainly IS harder to cheat. That doesn't mean that some competitors haven't got better at cheating. Doubtless they have. But on a point of fact, Fred is correct.