Pro cycling has tried to tighten up its doping detection processes in the past decade. In 2001 or 2002, it introduced a urine-based test for one of the biggest scourges in the sport, artificially synthesized EPO, a hormone used to boost red blood cell production. In 2008, it launched biological passports, a method for testing markers in an athlete's blood in search of statistically anomalous spikes.
Has it worked?
No one knows for sure, but one measurable difference is that pro cyclists have slowed down. This article analyzes results of biological passports in pro cycling and points out a decrease in the number of anomalous results since these tests have gone into place. In Lance Armstrong's heyday, an oft-quoted magic number that a cyclist needed to attain to ascend the podium at a grand tour was 7 W/kg. But the scientists behind this article find that figure to be beyond the reach of a clean cyclist.
That all began with the hypothesis that the power output achievable without doping was limited and could be predicted based on physiology, and that any cyclist who went above this on a long finishing climb in the Tour was probably doing so with the benefit of doping! That "limit", I suggested, was about 6.2 W/kg, a climbing power output that was very common in the 1990s and early 2000s, but which has NOT been seen since about 2006.
In this Finnish cycling forum, someone published what I believe are top-ranked average power outputs for cyclists racing grand tours from 2000 on (if you can read Finnish and translate, let me know; Chrome's Google Translate function made a mess of the formatting). The last cyclist to achieve an average power output of 6 W/kg or higher was Alberto Contador in the 2009 Tour de France. He won this year's Vuelta Espana with a power output of 5.88 W/Kg.
It's not definitive. Anomalous spikes in energy late in mountain stages would still seem suspicious. But anecdotally, we have seen fewer of those. Many people found the Tour de France boring this year because we did not have as many late mountain stage duels between the race leaders, as in years past. Is clean cycling doomed to be less dramatic a spectacle?
Whether it's because cyclists are racing clean now, or whether they've had to significantly cut back their doping, is unclear. They are measurably slower.
I personally believe that at least half the professional athletes I watch on TV across all sports are on some banned substance of some sort. I thought this during the Olympics, and I think this whenever I watch any professional sporting match (this is just the latest anecdotal evidence). While many of the athletes who've fingered their peers are not seen as trustworthy because they themselves doped, I personally suspect so many athletes dope that it's unlikely that it's clean athletes will be the whistleblowers. The threat of retaliation for a clean athlete who is still competing amidst a pool of dopers is high, but once someone's already been caught and banned, they have much less career risk.
If there's one lesson of economics that has proven solid over the years, it's the theory of incentives. Considering the minuscule odds of succeeding and the power-law distribution of income in professional sports, the economic incentives for doping are enormous, and selection bias would argue that the people we do get to see succeeding on TV are disproportionately weighted towards those who have used such substances. Even if the physical edge granted by such substances is small, the placebo effect and mental edge may be just as valuable. In Tyler Hamilton's book, Lance Armstrong is constantly on edge over what new doping techniques other cyclists might be using to achieve an edge over him.
The larger question at play is whether the social norm of sports as a competition between "clean" athletes competing on some some arbitrarily defined level playing ground is outdated or perhaps even a pipe dream. If clean competition is an unattainable ideal, a farce we've believed in for decades and decades, how far are we prepared to go, how much money are we prepared to spend, to chase after it? Is the reinforcement of fair play in sports so powerful an idea because we think it affects the moral fabric of the rest of society?