Price ceilings — a legal maximum price; when binding, they create shortages and non-price rationing (queues, waiting lists, black markets).

Price floors — a legal minimum price; when binding, they create surpluses (e.g. unemployment under a minimum wage).

Binding vs non-binding — only a ceiling below equilibrium or a floor above equilibrium actually changes the market.

Textbook cases — ice-cream ceiling, 1970s gasoline lines, rent control (short run vs long run), minimum wage.

Taxes create a wedge — buyers pay more, sellers receive less, quantity falls; legal incidence does not determine economic incidence.

Tax incidence & elasticity — the less elastic side of the market bears more of the tax burden.

Policy trade-offs — controls and taxes involve equity vs efficiency; evaluate with supply-and-demand graphs.