The difference between a public good and a private good
A private good gets used up when one person consumes it, and sellers can stop others from having it. A public good does neither — everyone can benefit at once, and no one can be excluded.
Real World
A Netflix subscription is a private good — it is excludable (you need a paid account) and partially rival in a household sense — contrasting sharply with a public fireworks display, which anyone nearby can watch without reducing others' enjoyment.
Exam Focus
Construct a 2×2 rivalry/excludability grid in your answer to classify goods clearly — examiners reward structured application of both criteria.
Price Elasticity of Demand
PED = % change in quantity demanded ÷ % change in price
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