> Are you saying that the likelihood of slacking off is higher for certain groups than others?

No, and I have no idea how you can misread my comment to mean that. What I'm saying is that most people don't want to work 70 hours a week. But most people would very much like the pay that you get from working 70 hours a week. If you allow them to choose both sides individually, I'm pretty sure they'd choose the low input and high output.