You can even go further: tell your employees that you'll be sending out fake test bribe offers, which they'll be expected to report, and that they'll be rewarde

You can even go further: tell your employees that you'll be sending out fake test bribe offers, which they'll be expected to report, and that they'll be rewarded for doing so. Similar to how IT in many large companies nowadays runs internal phishing tests. That changes the risk/reward, so while every reported bribe is a nice cash bonus, accepting any received bribe becomes significantly riskier, and by 'practicing' bribe reporting it becomes the default reaction.