I think those of us who teach economics face a regular problem - teaching about supply, demand and price. The concepts themselves seem obvious and simple. But start changing things and the students can go from acceptance to rejection.
This post on The Money Illusion blog (HT to Greg Mankiw for the pointer) examines how easily we can get confused by what seems to be a simple process. The comments are also worthwhile.
My experience has been students frequently have a rough time in knowing when to "move the curve" and when to "move along the curve" in their analysis. There are other factors: availability of acceptable substitutes, elasticity of demand, changes in income, etc. that can play a role, but if the students don't make the first choice correctly, thinking about the rest may not do them much good.
I'd be interested in your comments. Do you have trouble with these basic ideas when teaching your students?
This post references the following Keystone Economic Principles:
1. We all make choices.
9. Prices are determined by the market forces of supply and demand… and are constantly changing.