I understand work ethic to be a better predictor of wealth than intelligence. You can imagine a lots of smart slacker not living up to their potential.
An interesting study would be: is work ethic inherited (either genetically or culturally). It would be another confounder here, I think.
Probably not everything, but I believe it could be correlated with testosterone. I'm sure that has a genetic, diet, and environmental component to it. So right away I can say: yes.