Idiocracy. If you haven’t seen this, I recommend it. On the one hand it seems to explains a lot about the modern world, on the other the very name of the movie has entered the modern lexicon so you need to know it for cultural literacy. Here is the vital opening scene:

There might be something to this. Here is a peer-reviewed study comparing IQs of Victorian time with today, and it shows a drop of fourteen IQ points since Victorian times: “These findings strongly indicate that with respect to [IQ], the Victorians were substantially cleverer than modern Western populations.”