The phrase "effective deterrent" means something that discourages or prevents people from doing something by being strong and successful at stopping or punishing them. Full definition
Starting at $ 180, it's a very cost - effective deterrent against cosmetic and structural problems that can arise from excess moisture. (moneysense.ca)
This power of exposure is a far more effective deterrent in many countries, including our own, than the court systems that deliver judgment and not necessarily justice. (nigeriapoliticsonline.com)