Why do politicians try to ban things they don't like?  Moreover, why do so many people think that banning things is an effective way to change other people's behavior?  This week, we explain why banning things just doesn't work and why you should instead focus on reducing demand for the thing you don't like. We explore three specific political topics that relate to this supply and demand problem.  Here are some graphs to help you visualize what we mean when we're talking about reducing supply or demand for something.