Your friend decides to leave school so that they can earn more income by working more hours at their job. Some years later, you run into them, and they tell you about a promotion they missed out on due to not having a degree. Which of the six core principles of the economic way of thinking does this illustrate? The Consequences of Choices Lie in the Future People Gain When There is Voluntary Trade People Respond in Predictable Ways to Incentives. Economic Systems Influence Choices and Incentives