The engine

Compounding: returns on returns#

Compound interest is the only free lunch that also pays for dessert.

In year one you earn a return on your money. In year two you earn a return on your money and on last year’s return. At first that’s pocket change. At the end it’s the main event. Which is why starting early beats starting big.

Guess first

€300 a month for 40 years at an assumed 7% a year. What do you end up with?

Show me

Look at the last two rows. Ten more years cost you €36,000 of your own money and add about €390,000 of value. The engine wants time far more than it wants fuel.

What a share is#

A share is a piece of a company. Own it, and you own a slice of the factories, the software, the brands and the future profits.

You earn in two ways: the company pays out part of its profit as a dividend, and the share price rises when the business becomes more valuable.

Behind the ticker symbols are people who get up in the morning and try to sell more and spend less. That’s where the return comes from. It’s not a casino, unless you insist on playing it like one.

Fun fact: Marx wanted the workers to own the means of production. Turns out that takes a broker account and a savings plan. No revolution, no central committee, and the supermarket shelves stay full.

Why broad diversification#

A single company can go to zero. Famous names included.

Picking the winners in advance is hard, even for the professionals who do it full time and charge you for the attempt. So I wouldn’t try. I’d buy all of them.

The same goes for countries. Wherever in Europe you live, your home stock market is a small slice of the world’s companies. Your salary, your pension claim and probably your flat already depend on that one country. Your shares don’t have to.

Own thousands of companies across countries and industries, and a single failure costs you a fraction of a percent. What’s left is the risk of the market as a whole. You can’t diversify that away, and it’s exactly the risk you get paid for.

Index funds and ETFs#

An index is a list of companies with rules. The MSCI World, for example, contains 1,280 large and mid-sized companies from 23 developed countries (August 2026).

An index fund buys what’s on the list, in the same proportions. Nobody gets paid to have opinions, so it’s cheap.

An ETF is an index fund that trades on the stock exchange. You buy it through a broker like a share, or by monthly savings plan.

Guess first

The MSCI World covers 23 developed countries. What share of the index is US companies?

Show me

Risk is not volatility#

Volatility is how much the price swings. Risk is the chance that you don’t reach your goal, or that you lose money for good.

Two very different things:

• A global equity fund is volatile. It can lose half its value in a crash. Over long periods it has recovered every time so far.
• A savings account isn’t volatile at all. But if it earns less than inflation for 30 years, you lose purchasing power with certainty. Calmly, quietly, guaranteed.

For money you need in two years, volatility is a real risk. For money you need in 25 years, the bigger risk is not being invested.

Time horizon#

A rule I find useful: money you need within the next five years has no business in shares. Money you won’t touch for 15 years or more can take the swings.

Everything in between is a judgement call. You’ll make it in the next level.

What history says, and what it doesn’t#

From the end of 1987 to August 2026, the MSCI World returned 9.08% a year, measured in US dollars, with dividends reinvested, before costs and tax.

In euro, zloty or francs the figure for each single year looks different, because exchange rates move too. The pattern doesn’t change.

Nice. Now the other half: the same index lost 57.46% between 31 October 2007 and 9 March 2009.

Those two numbers are a package deal. The long-run return is what you get paid for sitting through the drops. Historical returns are not promises, and the next decades can be better or worse. I think we’re closer to the next big drop than most people like to hear, so for planning I’d use a lower number than history and be pleasantly surprised if reality beats it.

Try it right here: set the return to 5% instead of 7% and see what’s left.

This lesson is education, not investment, tax or legal advice.

Next level: you assemble the machine – broker, fund, allocation and a savings plan that runs by itself.

Mission

• Run the compound interest calculator with your monthly amount for 10, 20 and 30 years
• Run it again with 5% instead of 7% and note the difference. That’s your reality check
• Open the fact sheet of a global equity index and find four things: number of companies, largest country, the weight of your own country, maximum drawdown

Quiz · 3 questions

Q1 Why does starting early matter so much with compounding?

Because the market has a soft spot for young investorsBecause returns earn returns, and the effect grows with every yearBecause fees are lower in the first years

Q2 What does broad diversification protect you from?

From market crashes. Nothing does thatFrom inflationFrom the failure of single companies or industries

Q3 Which statement about risk and volatility is correct?

Volatility is price movement, risk is failing to reach your goalAn investment without volatility has no riskVolatility is only a problem for people in suits

Sources#

• MSCI – MSCI World Index (USD) fact sheet, 31 August 2026: constituents, country weights, gross returns since 31 December 1987, maximum drawdown

level 3

Done reading?

Tick the mission, answer the quiz, then claim your XP. Or just claim it, I’m not your teacher.

Complete level · +100 XP Level 4: Build the machine

Education, not advice. I don’t know your situation, and past returns promise nothing. Check my numbers, then make your own call. You’re a grown-up.