Prerequisites

This book assumes nothing about economics. It assumes a small amount about math, charts, and reading. This page lists the prerequisites explicitly so you know what you need before you start — and so you can shore up any gaps before they become a problem.

Math

You need:

  1. Basic arithmetic. Addition, subtraction, multiplication, division. Calculating percentages. Calculating percentage changes (the change divided by the original, times 100). If you can compute a 15 percent tip on a restaurant bill, you have enough.
  2. Basic algebra. Solving for x in a simple equation like 2x + 3 = 11. Substituting one variable into another equation. Manipulating equations to isolate a variable. If you can solve p = 10 − 2q for q, you have enough.
  3. The ability to read and interpret graphs with x and y axes. This includes recognizing the slope and intercept of a straight line, identifying where two lines intersect, and reading values off a curve. Most of the book's "math" is graphical, not algebraic.

You do not need:

  • Calculus. Derivatives, integrals, partial derivatives, optimization with constraints — none of this is required. Where calculus is mentioned at all, it appears in optional sidebars marked as previews of intermediate-level study.
  • Statistics. Mean and median appear without much fanfare; there is no hypothesis testing, no regression analysis, no probability theory beyond intuition. (If you want a serious treatment of statistics, see Introductory Statistics in the DataField series.)
  • Trigonometry, linear algebra, differential equations, or any other "advanced" math.

If your algebra is rusty, Appendix A — Graphing and Algebra Review in appendices/ is the refresher you want. Read it before Chapter 5 if you feel uncertain. It takes 30–45 minutes.

Reading

You should be comfortable reading non-fiction prose at roughly the level of a serious newspaper or magazine — The Atlantic, The Economist, The Wall Street Journal, The New York Times, Bloomberg Businessweek. The book is written more conversationally than a typical textbook, but it doesn't talk down to you. Some chapters are 10,000+ words and reward sustained attention.

If English is not your first language and you find economics-specific vocabulary challenging, the Glossary in appendices/glossary.md defines every key term in the book in plain language. Look up anything you don't recognize. You will not lose points (or status, or the respect of any reader of this preface) by looking up a word.

Quantitative reasoning

You should be comfortable with — or willing to develop comfort with — the following kinds of quantitative thinking:

  • Comparing two numbers. "Median household income in Millbrook is $48,000; the national median is $74,000. Millbrook is poorer than the national average." That kind of comparison.
  • Reading a percentage. "Inflation rose 7.0 percent in 2022." What does that mean? It means prices in 2022 were on average 7 percent higher than in 2021.
  • Reading a chart. A line chart of GDP over time. A bar chart of unemployment by state. A scatter plot of education and income. You should be able to look at a chart, identify the axes, identify the units, and identify the pattern.
  • Estimating orders of magnitude. "The federal budget is about $6 trillion. The US economy is about $25 trillion. So the federal budget is about a quarter of the economy." That's an order-of-magnitude estimate. You don't need to be precise; you need to know whether something is closer to a million, a billion, or a trillion.

Chapter 4 — How to Read Economic Data — is designed to develop these skills if they aren't strong already. Don't skip it.

Curiosity

This is the most important prerequisite, and the one we cannot teach. You need to be willing to ask "why?" and willing to be unsatisfied with the first easy answer.

  • Why does a coffee at the campus café cost $4.50?
  • Why are some countries rich and others poor?
  • Why do politicians from opposite parties often disagree about whether a tax cut "works"?
  • Why does the price of housing keep rising in some cities and not others?
  • Why did inflation spike in 2021 and then fall again, and why couldn't anyone agree about why?

If those questions feel boring, this book is not going to fix that. If they feel interesting — even a little — you have everything you need.

What you don't need

You do not need:

  • A laptop, though one helps if you want to play with data.
  • Software, though a spreadsheet (Google Sheets, Excel, LibreOffice Calc) is useful for the data-literacy exercises.
  • A library, though a library is one of the best places to read this book.
  • A study group, though one helps. Doing exercises with friends is more fun and more educational than doing them alone.
  • An economics professor, though one helps even more.
  • Money. The book is free.

A short self-check

Before starting Chapter 1, see if you can answer the following five questions. If you can answer at least three of them, you are ready. If you can't, the relevant prerequisites are flagged.

  1. What is 25 percent of 80? (arithmetic — answer: 20)
  2. If a price rises from $10 to $12, what is the percentage change? (percentages — answer: 20%)
  3. Solve for q: p = 50 − 2q, when p = 30. (algebra — answer: q = 10)
  4. Look at a line chart showing US GDP from 2000 to 2024. The line slopes upward overall but dips sharply in 2008–09 and 2020. What do those dips represent? (chart reading — answer: the Great Recession and the COVID recession)
  5. Why is some inequality "good" and some inequality "bad"? (curiosity and reasoning — there is no single right answer; the question is whether you can articulate a thoughtful response. The book will help you sharpen your thinking on questions like this.)

If you struggled with 1–3, work through Appendix A before Chapter 5. If you struggled with 4, do the exercises in Chapter 4 carefully. If you struggled with 5, you are in for a treat — the entire book is built around questions like this.

A final note

Prerequisites are about preventing frustration, not about gatekeeping. If you bring curiosity, basic math, the ability to read patiently, and the willingness to look things up when you don't recognize them, you have everything you need. The rest is on us — and we have done our best.

Welcome to economics.