Which of the following is NOT an identity?
Net worth equals assets minus liabilities. The amount bought equals the amount sold. The amount of a product that people will buy depends on the price of the product. Profit is the difference between revenues and costs.
In a zero-sum game whatever someone earns is exactly matched by something that someone else losses. There are also positive-sum and negative-sum situations. In a positive-sum situation, the amount won exceeds the amount lost. In a negative-sum situation, the amount lost exceeds any winnings. An example of a negative-sum game is:
poker. marriage. free trade. war.