Twelfth Grade · History · week 23

Demand: the buyer's side

Explain the law of demand and the shifters of demand (income, tastes, substitutes, expectations).

Demand is how much buyers will purchase at each price. The law of demand: as price falls, quantity demanded rises — cheaper things get bought more, both because each buyer stretches further and because new buyers join in. Plotted, demand slopes downward. Supply's mirror twin.

The same discipline applies: price changes move you ALONG the demand curve; everything else shifts it. The big shifters: income (raises demand for most goods), tastes and trends, prices of substitutes (chicken pricier → beef demand rises) and complements (cheaper consoles → game demand rises), number of buyers, and expectations (believe prices rise tomorrow, buy today). A viral video doesn't change today's price — it shifts the whole curve right.

📋 For the grown-up teacher
Teach it (10–15 min):
  • Mirror last week deliberately: same drills, buyer's chair. The symmetry is the lesson.
  • Their own demand curve: for a real item, how many per month at $30? $15? $5? Plot it.
  • Sort substitutes vs complements with household pairs: butter/margarine, phones/cases, buses/cars.
  • Catch a shifter in the wild this week: a trend, a sale rush, pre-storm stocking. Name which shifter.
Talk about it:
  • Why do sellers run sales at all?
  • What could make you buy MORE of something at the SAME price?
  • Substitute or complement: printers and ink?

Mastery looks like: They state the law of demand, and classify shifter scenarios (income/taste/substitute/complement/expectation) correctly.

Common stumbles: Confusing "demand" (the whole curve) with "quantity demanded" (one point); reversing substitutes and complements.

Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
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