World 3 · Money psychology · Lesson 12 of 12

Overconfidence and optimism bias

Most people think they are above average and that bad things happen to others. Money pays for both.

6 min read · Level: Practical · Free — no account needed to read

The idea

Overconfidence is believing you know more, or can do better, than you actually can. Most people rate themselves as above-average drivers, and many investors believe they can pick winners or time the market better than others. Confidence feels good and helps people act, but in money it often leads to trading too much, taking concentrated risks and ignoring warning signs.

Optimism bias is its companion: the belief that bad things are more likely to happen to other people. It leads people to skip emergency savings, underinsure, and assume their income will keep rising and their plans will go to schedule. Plans nearly always take longer and cost more than expected.

Why it matters

Overconfidence and optimism are costly because they remove the margin of safety. Planning for things going somewhat worse than you hope protects you when — as usually happens — they do.

A real example

The situation

Leo is sure his renovation will cost what the builder quoted and take six weeks. He plans with no extra money set aside.

What happened

The work takes eleven weeks and costs a third more. Leo has to borrow at a high rate to finish it. On his next project, he adds a generous buffer to both time and money from the start.

The takeaway

Planning for the likely overrun would have been cheaper than paying for it after.

How people actually behave

People remember their successes and explain away their failures, which keeps confidence high. They also plan from the best case, imagining how things will go rather than how similar things usually went.

Common mistakes

• Believing you can consistently outguess markets or pick winners.
• Planning projects and budgets from the best case.
• Skipping safety nets because bad luck “won’t happen to me”.

Think it through

You plan a move, a wedding or a renovation. Your budget adds up exactly to the money you have.

What usually happens to projects like this, and what would you change about the plan knowing that?

Questions to think about

• Where have you been most confident about money, and how did it turn out?
• What plan of yours would look different if you assumed it will cost a quarter more?

Try it: The outside view

1. Pick a plan with a cost or a deadline.
2. Instead of imagining how it will go, find out how similar plans usually went for others.
3. Adjust your budget and timeline to match that, not your best case.

Words in this lesson

• Optimism bias — The tendency to believe bad things are more likely to happen to other people than to yourself.