For my students out there reading this, please pay attention to the lecture or I'll switch the WiFi off.
No, seriously, take a look at this post by John Quiggin (via others). Make sure you can answer questions like this for the mid-term. Also, to the extent that you can, you can also see evidence that you might be outperforming many economics PhDs. (No wonder it is so hard for you to get substitutions for economics in the MBA course!)