Supply and demand, elasticity, market structures and macroeconomic indicators.
Economics studies how people, businesses and governments make choices when resources are limited. Microeconomics looks at individual markets through supply, demand, costs and competition; macroeconomics looks at the whole economy through output, inflation, unemployment and policy.
Graphs and simple formulas carry most of the reasoning. Price elasticity of demand compares the percent change in quantity to the percent change in price, the spending multiplier is , and real GDP removes the effect of inflation from nominal figures. Each model rests on assumptions worth stating explicitly.
Economic reasoning appears in business strategy, public policy, personal finance and the news. It explains why prices change, how interest rates affect borrowing and why some policies have unintended effects, and it is useful preparation for business, law and political science.
Micro and macro foundations with graphs and calculations. (High school)
Prices in a competitive market come from the interaction of buyers and sellers. The demand curve slopes down: as price falls, people want more. The supply curve slopes up: as price rises, producers offer more. The equilibrium is the price at which quantity demanded equals quantity supplied, so there is no shortage or surplus.
Price elasticity of demand measures how strongly quantity demanded responds to a price change: the percentage change in quantity divided by the percentage change in price. If the absolute value is greater than 1, demand is elastic; less than 1, inelastic; exactly 1, unit elastic.