Microeconomics basics: A Practical Course with Freya Larsen

Start with the purpose

Place Microeconomics basics inside a realistic personal-finance, operations, or workplace decision. Name the result a learner is trying to produce and the constraints that make the skill useful.

How Microeconomics basics actually works

These are the load-bearing ideas. Everything later in the course is an application of one of them, so it is worth reading slowly and returning to when something stops making sense.

• Opportunity cost is the real cost. The cost of any choice is the value of the best alternative given up, which is why an unpaid internship is not free. Sunk costs, already spent and unrecoverable, are correctly excluded from every forward-looking decision.
• Elasticity decides what price changes do. Price elasticity of demand is the percentage change in quantity divided by the percentage change in price. Where the magnitude exceeds 1 demand is elastic and a price rise cuts revenue; below 1 it is inelastic and a price rise raises revenue.
• Optimise where marginal revenue equals marginal cost. Profit is maximised at the output where the last unit adds exactly as much revenue as it adds cost. Average cost tells you whether to be in the business at all; marginal cost tells you how much to produce.

Misconceptions worth clearing early

Each of these is common, understandable, and expensive to leave in place. Recognising them now saves rework later.

• Treating sunk costs as reasons to continue. Abandoning a project feels like wasting everything already spent on it. Fix: Ask only whether future benefits exceed future costs; the past spend is identical under both options and cancels out.
• Assuming the demand curve shifts when price changes. Any drop in sales after a price rise looks like demand falling. Fix: A price change moves you along the curve; only non-price factors such as income, tastes, or substitute prices shift the curve itself.
• Comparing figures from different periods or definitions. Both numbers look valid in isolation. Fix: State the period and definition next to every figure before comparing them.

Build the mental model

Connect the key terms as a process rather than a word list. Use this sequence: organize the records, calculate or compare options, document assumptions, and recommend an action.

Catch the common miss

Compare a surface-level attempt with one that shows complete records, sensible assumptions, accurate calculations, and a usable recommendation. Explain the single difference that matters most.

Watch the whole process

Trace a model from the initial prompt to a decision worksheet and practical plan. Mark each point where the learner must observe, choose, or verify rather than act automatically.

Worked example: Testing a price rise from 10 to 12 with the midpoint formula

Follow each step and predict the next before you read it. Predicting first is what turns a demonstration into practice.

1. Weekly quantity sold falls from 100 units to 80 units.
2. Percentage change in quantity is -20 / 90 = -0.222, using the midpoint average of 90.
3. Percentage change in price is 2 / 11 = 0.182, using the midpoint average of 11.
4. Elasticity is -0.222 / 0.182 = -1.22, so demand is elastic.

Revenue confirms the reading: 10 × 100 = 1,000 before and 12 × 80 = 960 after, so the elastic response made the price rise unprofitable.

Where this usually goes wrong

Watch for these while you work through the demonstration rather than afterwards.

• Treating sunk costs as reasons to continue. Abandoning a project feels like wasting everything already spent on it. Fix: Ask only whether future benefits exceed future costs; the past spend is identical under both options and cancels out.
• Assuming the demand curve shifts when price changes. Any drop in sales after a price rise looks like demand falling. Fix: A price change moves you along the curve; only non-price factors such as income, tastes, or substitute prices shift the curve itself.
• Comparing figures from different periods or definitions. Both numbers look valid in isolation. Fix: State the period and definition next to every figure before comparing them.

Practice with scaffolding

Repeat the model with one detail changed. Keep the prompts visible and say or write the reason for each choice before continuing.

Check before feedback

Use complete records, sensible assumptions, accurate calculations, and a usable recommendation as the quality test. Make one self-correction before asking the tutor to review the result.

Read the situation

Translate the scenario into a clear task. Separate facts, assumptions, constraints, and information that is interesting but not relevant to Percentages and rates.

Choosing well under real constraints

Applied work is mostly judgement under limits: less time, less information, and more competing goals than a textbook example allows. These are the decision rules that hold up in practice.

• Two options look similar on price: Compare total cost including delivery, fees, and time, not the quoted figure.
• A number surprises you: Trace it back to its source before acting; surprising figures are often definitional, not real.
• You must recommend under uncertainty: Recommend the option that stays acceptable if your main assumption is wrong.

Reading the situation before acting

Before choosing an approach, state three things explicitly: what result the situation actually requires, which constraints are fixed rather than preferences, and what evidence would tell you the approach is working. Skipping this step is the most common reason competent work solves the wrong problem.

• Opportunity cost is the real cost. The cost of any choice is the value of the best alternative given up, which is why an unpaid internship is not free. Sunk costs, already spent and unrecoverable, are correctly excluded from every forward-looking decision.

Practitioner notes

Small pieces of working knowledge that rarely appear in introductory material.

• Estimate elasticity from your own historical price changes before trusting a published category average, because segments within a category differ enormously.
• When comparing two options, write the opportunity cost of each one out explicitly; the option that looks cheapest in cash frequently is not once the foregone alternative is named.

Compare real options

Generate two workable approaches and test both against the purpose. Do not hide the tradeoff; name what each option improves and what it gives up.

Make the reasoning visible

Produce a decision worksheet and practical plan and attach a short decision note. The note should make the result auditable, not merely confident.

Use the rubric, not a feeling

Review the work for complete records, sensible assumptions, accurate calculations, and a usable recommendation. Record evidence for each judgment so feedback points to something observable.

Diagnostic checklist

Run this before you revise anything. Diagnosing first prevents the common failure of polishing the parts that were already fine.

• Check: Treating sunk costs as reasons to continue — is this present in your work?
• Check: Assuming the demand curve shifts when price changes — is this present in your work?
• Check: Comparing figures from different periods or definitions — is this present in your work?
• Check: Confusing profit with cash — is this present in your work?

The quality bar

This is what finished work looks like in this field. Use it as the standard for your revision rather than a general sense of improvement.

• Every figure is traceable to a source and a period
• Assumptions are stated where a reader can test them
• The recommendation names its main risk and what would change it

Diagnose before editing

Name the symptom, then ask what decision or missing step produced it. Choose the cause you can address rather than changing everything at once.

Revise and compare

Make one purposeful revision and compare the two versions. Keep the change only if it improves the intended result without creating a larger problem.

Define a finishable brief

Choose a specific audience, result, and boundary for the Chart interpretation capstone. Reduce scope until the project can be finished and reviewed in one focused cycle.

Bringing the parts together

A capstone is judged on coherence, not on the number of techniques it includes. Return to the core ideas and make sure the work demonstrates them rather than decorating them.

• Opportunity cost is the real cost. The cost of any choice is the value of the best alternative given up, which is why an unpaid internship is not free. Sunk costs, already spent and unrecoverable, are correctly excluded from every forward-looking decision.
• Elasticity decides what price changes do. Price elasticity of demand is the percentage change in quantity divided by the percentage change in price. Where the magnitude exceeds 1 demand is elastic and a price rise cuts revenue; below 1 it is inelastic and a price rise raises revenue.
• Optimise where marginal revenue equals marginal cost. Profit is maximised at the output where the last unit adds exactly as much revenue as it adds cost. Average cost tells you whether to be in the business at all; marginal cost tells you how much to produce.

Standards that make the work credible

These are the marks of work that would be taken seriously by someone who does this professionally.

• Every figure is traceable to a source and a period
• Assumptions are stated where a reader can test them
• The recommendation names its main risk and what would change it

Practitioner notes

Small pieces of working knowledge that rarely appear in introductory material.

• Estimate elasticity from your own historical price changes before trusting a published category average, because segments within a category differ enormously.
• When comparing two options, write the opportunity cost of each one out explicitly; the option that looks cheapest in cash frequently is not once the foregone alternative is named.

Build with checkpoints

Plan foundation, first draft, verification, and revision milestones. At each checkpoint, save evidence instead of relying on memory.

Present and continue

Present a decision worksheet and practical plan with a concise rationale. Use the final rubric to choose one strength to retain and one next practice target.