Supply and demand grapher

When demand increases, price and quantity both rise; when supply increases, price falls and quantity rises. A change in the good’s own price is a movement along a curve, not a shift. A price ceiling below equilibrium causes a shortage, and a floor above it causes a surplus. Predict each change, then check it on the graph.

One-shift rules

  • Demand increases (shifts right): price rises, quantity rises.
  • Demand decreases (shifts left): price falls, quantity falls.
  • Supply increases (shifts right): price falls, quantity rises.
  • Supply decreases (shifts left): price rises, quantity falls.

Two-shift rules

  • Demand and supply both increase: quantity rises; price change is indeterminate.
  • Demand and supply both decrease: quantity falls; price change is indeterminate.
  • Demand increases and supply decreases: price rises; quantity change is indeterminate.
  • Demand decreases and supply increases: price falls; quantity change is indeterminate.

What shifts each curve

  • Demand shifters: income (normal goods), prices of substitutes and complements, tastes, expectations, number of buyers.
  • Supply shifters: input costs, technology, number of sellers, expectations, taxes and subsidies.
  • A change in the good’s own price causes a movement along a curve, not a shift.

Price controls

  • Price ceiling (legal maximum) below equilibrium: shortage, because quantity demanded exceeds quantity supplied.
  • Price floor (legal minimum) above equilibrium: surplus, because quantity supplied exceeds quantity demanded.
  • A ceiling above equilibrium or a floor below it is not binding and has no effect.

The graph in this lab is a stylized straight-line model, not real market data. Price is on the vertical axis and quantity on the horizontal axis.

GED Social Studies facts (checked 26 October 2026)

  • The Social Studies test lasts 70 minutes, including 2 minutes of instructions and final review, with no break (GED.com).
  • Question types: multiple choice, drag and drop, fill in the blank, select an area and drop-down (GED.com).
  • Content: civics and government 50%, U.S. history 20%, economics 15%, geography and the world 15% (GED Testing Service assessment guide).
  • GED.com says the Social Studies test is not a memorization test: you use the information given to draw conclusions.
  • You pass a GED subject with a score of 145 on the 100 to 200 scale. Lab results here are practice only and are not GED scores.

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