Thinking Like an Economist: Part 2
Unit 1 · Lesson 1.4 · Last updated May 20, 2026
A 45-minute lesson introducing the marginal and interdependence principles of economic thinking, with practice applying all four principles to real-world decision making.
Overview
In this lesson, students learn about the two remaining principles of economic thinking — the marginal principle and the interdependence principle — and have a chance to practice applying all four principles to decision making. Explicit connections are made between these principles and the primary activity in Lesson 1.2. Note: This lesson assumes that students were introduced to the first two principles of economic thinking in Lesson 1.3.
Video Tutorial
Learning Objectives
- Describe the marginal principle and the interdependence principle and explain the role they play in decision making.
Materials
- Instruction Slides (display during class period)
- Activator Article (1 copy per student)
- Student Handout (previously distributed in Lesson 1.3)
- Retrieval Practice (1 copy per student)
Lesson Sequence
Slides 2–4
- Display Slide 2. Distribute 1 copy of Activator Article to each student. Allow 3 minutes for students to individually follow the instructions on the slide. After 3 minutes, ask students to share their responses with a peer, then debrief as a class. Note: This activity is designed to allow students to practice for the Unit 1 summative assessment.
- Proceed to Slide 3. Tell students to retrieve their 1.3 Student Handout (Thinking Like an Economist) distributed in Lesson 1.3. Remind students that in the previous lesson they learned about the first two principles of economic thinking.
- Display Slide 4 and introduce the learning objective for the lesson.
Slides 5–26
- Proceed through Slides 5–6 to transition to the marginal principle. On Slide 6, click to introduce the marginal principle. Note: The anchor question "One more?" on Slide 6 is a helpful tool for students. Remind students they may continue adding notes to Student Handout throughout the lesson.
- Display Slide 7. Ask students to recall their choices from the primary activity in Lesson 1.2 and answer the questions on the slide with a peer. Click to explain that students were applying the marginal principle to their decision making.
- Proceed to Slide 8. Click to guide students through the decision-making graphic illustrating how the marginal and cost-benefit principles are applied together.
- Display Slide 9. Explain how thinking at the margin supports the maximization of benefits.
- Proceed to Slide 10. Direct students to discuss their answers with a peer to assess their ability to identify choices requiring marginal decision making. Proceed to Slide 11 to reveal the answers.
- Display Slide 12. Use the text on the slide to emphasize that not all decisions involve the marginal principles.
- Advance to Slide 13. Click to introduce the interdependence principle. Note: The anchor question "What else?" on Slide 12 is a helpful tool for students.
- Use Slides 14–15 to illustrate examples of the interdependence principle from Lesson 1.2 and students' lives. Pause between slides to allow students to discuss their answers with a peer, then debrief as a class.
- Advance through Slide 16. Tell students they will now practice explaining how the principles of economic thinking apply to decisions.
- Use Slides 17–21 to guide students through the process of identifying and explaining how the principles of economic thinking apply to a scenario.
- Proceed to Slide 22. Remind students to consult the anchor questions on Student Handout as they collaborate with a peer to identify and explain how each principle applies to the scenario. Allow approximately 3 minutes for pairs to analyze and discuss. Conduct a class discussion to debrief using Slide 23.
- Advance to Slide 24 and repeat step 14. Use Slide 25 to debrief.
- Display Slide 26. Use the text on the slide to emphasize that not all decisions involve the marginal principle.
Slides 27-28
- Progress to Slide 27. Tell students they will work alone for this portion. Distribute 1 copy of Retrieval Practice to each student. Explain that it is a low-stakes opportunity to assess their current level of understanding.
- Display Slide 28. Allow students 10 minutes to complete Retrieval Practice, including the portion calling for "Reinforcement Readings." Note: Students are given all sections of Reinforcement Readings to provide additional examples of each principle of economic thinking.
- Collect Retrieval Practice and review for common misconceptions and gaps in understanding to address at the start of the following class.
Aligned Standards
Voluntary National Content Standards in Economics
Standard 2 Decision-Making
What Educators Are Saying
This lesson dovetailed nicely with 1.2 and 1.3!
High School Economics Teacher, Arizona
Students were also able to relate. I also like the scenarios offered so students can apply the economic concepts.
High School Economics Teacher, Arizona
It was well organized.
High School Economics Student, Arkansas