Change of Demand Curve

令 xx 表示商品，那么其 Demand Curve 可以表示为

Qxd=a+bPxd+… Q^d_x=a+bP^d_x+\dots

Increase in Demand

直线向右上移动，可以是向上平移，也可以是向右平移

Movement
Movement
影响因素：Income
  • Normal Good
    • Income↑  ⟹  Qxd↑\text{Income}\uparrow \implies Q^d_x\uparrow
  • Inferior Good
    • Income↑  ⟹  Qxd↓\text{Income}\uparrow \implies Q^d_x\downarrow
影响因素：Population
影响因素：Price of Substitutes
Psubstitute↑  ⟹  Qxd↑ P_{\text{substitute}}\uparrow \implies Q^d_x\uparrow

当其他平替的价格上涨，消费者自然而然会转向价格更低的 xx

影响因素：Price of Complement
Pcomplement↑  ⟹  Qxd↓ P_{\text{complement}}\uparrow \implies Q^d_x\downarrow
影响因素：Expectation

The expectation of a higher (lower) price for a good in the future increases (decreases) current demand for the good.

影响因素：Tastes

Supply

Movement of Supply Curve
Movement of Supply Curve

Increase in Supply

Technology

Entry implies more sellers in the market increasing supply.
Exit implies fewer sellers in the market decreasing supply.

Sellers will supply less of a good if the price of an alternate good using the same inputs rises (and vice versa). (-)