Why is it bullshit - we are discussing cheating as a basic human behavior. I'm not promoting drug use as your handle implies, but responding to the question in terms of how many people here would dope. My point is that the empirical evidence indicates high prevalence of cheating across different settings is quite high, and so I think a large number of people would dope under the situation described.
Consider:
The year after Congress required that children 5 or older have Social Security numbers, the number of dependent exemptions dropped by 7 million.
In a 2005 survey (McCabe; Ethics and Behavior) – 70% of HS students admitted one or more instance of cheating on a test; 60% admitted plagiarizing a paper. Another study found that 80% of the highest achievers admitted to cheating on a test.
More recently, Fellers et al. (2009, Journal of Scientific Psychology) found that 95% of students at a midwestern university reported some form of cheating behavior in the previous 2 years. Can 95% of people find a way to live with themselves after cheating? It appears that they can.
Cheating in athletics is also common. A study of junior tennis players (who call their own game – whether a ball was in or not) – found high rate of cheating (Sorry – I can’t find the reference at the moment). Go to any HS dual or small invite indoor meet where there are few officials and see how many runners run inside the first lane. And the number of athletes taking supplements continues to increase. As a previous poster indicated, the more important the goal and the more invested one becomes in reaching the goal, the greater the internal push to cheat.
And finally, let's switch gears a bit and consider the high prevalence rate of Allderall – the “brain steroid” - among college students. In fact, here is another scenario for you:
You are in taking a critical course in your major and your grade affects your chances of getting into law school (or graduating with a high GPA and landing a great job). You get a B on test one; your friend gets a C. Your friend takes Allderall while studying for and taking the second test, even though it is not supplied by her physician. You get a B-. Your friend offers to get you some for the next test. You really need a high grade in the class. Do you take Allderal? And if you get an A and get into grad school or get a great job, can you live with yourself?