Einstein's 8th Wonder: Compound Interest and the Rule of 72 (2024)

Before we get started today, if you haven’t already seen it, check out my interview with Alex Langer of Sierra Madre. There could be quite an opportunity setting up with this silver mining company.

And if you haven’t read this piece on UK (and US) house prices yet, you might like it - it’s proved quite popular.

Right. The Eighth Wonder of the World …

Einstein's 8th Wonder: Compound Interest and the Rule of 72 (1)

How can you turn a tiny sum into a large one?

Speculate in small caps is one way. The problem is you risk losing your shirt.

There is another, safer path. All you need is time - lots of it - and some discipline.

You will often hear it said that time in the market is more important than timing the market. There is a lot of wisdom to the adage, though, in defence of timing, get it right and you gain significant advantage.

The underlying wisdom of the adage derives from the power of compounding, what Albert Einstein called the eighth wonder of the world. “He who understands it, earns it. He who doesn’t, pays it,” he is said to have said. (It is one of those attributed quotes, but it’s better coming from Einstein than anyone else, I suppose).

If I offered you a million quid upfront, or a magical penny that doubles in value every day for 30 days, would you take the million quid? I imagine you would.

You fool!

A penny that doubles every day would be worth over five million on day thirty.

But here’s the thing: it is the effect of compounding in the later stages that is breathtaking. The early stages are muted. Take that magical penny. On day 10, it’s only worth a fiver. By day 20 it’s north of five grand.

But it’s in the last three or four days that the vast sums are made.

Take a look at this table.

Einstein's 8th Wonder: Compound Interest and the Rule of 72 (2)

Compounding works even for relatively low annual returns. To benefit from it you have to start as early as you possibly can, re-invest everything you make and, ideally, keep adding. But it enables you to turn small sums into large ones. Just ask Warren Buffet.

This table shows the effects of compounding at different rates of return, but it assumes you don’t add to the initial pot. If you do that, the effects are more dramatic.

Einstein's 8th Wonder: Compound Interest and the Rule of 72 (3)

Tell your kids about compounding, and get them saving and investing. They’ll thank you.

To really benefit from compounding you also need to keep fees and taxes to a minimum. Thus the maximum gets re-invested. Avoid losses like the plague. Keep adding to the pot, and the compounding works even more in your favour.

There is a really cool tool here at Monevator, which allows you to see the effects. An initial deposit of £5,000, with £2,000 added every year and a 7% rate of return becomes half a million in forty years and a million in 50.

Invest just £2,150 every year at 7% and in fifty years you will have a million quid. But at the same rate over a fifteen year period to get to a million you would have to invest £33,800 - fifteen times as much.

The table below, courtesy of Visual Capitalist, demonstrates the maths.

Einstein's 8th Wonder: Compound Interest and the Rule of 72 (4)

There is also a useful predictive tool which can tell you how long it will take for your money to double, assuming you compound at a certain rate. It’s called the rule of 72.

Further to some correspondence with reader K the other day, I thought I should tell you about it.

Divide 72 by your annual rate of return and that will tell you the number of years it will take your portfolio to double.

Put in mathematical terms it looks something like this:

72 ÷ by rate of interest/return = number of years.

Let’s say you have a 5% annual rate of return. 72 divided by 5 is 14.4, so that’s how long it will take for your money to double: 14 years five months, give or take.

At 10% you will double your money every seven years.(The rule of 72 does not take inflation into account).

At the suppressed interest rates of the 2008 to 2021 period, it’s a very different story. Savings left in cash at 0.1% would take 720 years to double.

Of course, if you lose money, in a given year, it’s a very different story. Compound purists avoid losses like the plague, as we all should, and, most of the time, steer clear of cyclical sectors that can be prone to prolonged bear markets - unless they feel they can time them. That’s why compounding works well in conjunction with a diversified portfolio.

You can read more on portfolios here.

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Until next time …

Einstein's 8th Wonder: Compound Interest and the Rule of 72 (2024)

FAQs

Einstein's 8th Wonder: Compound Interest and the Rule of 72? ›

Divide 72 by your annual rate of return and that will tell you the number of years it will take your portfolio to double. Put in mathematical terms it looks something like this: 72 ÷ by rate of interest/return = number of years.

What did Einstein say was the 8th wonder of the world? ›

And this is where Albert Einstein comes into play. According to Einstein, “Compound interest is the eighth wonder of the world. He who understands it, earns it … he who doesn't … pays it.” At first this quote might seem like a bit of an exaggeration but the math behind it shows that it is not.

What is the rule of 72 in the wonder of the world? ›

The Rule of 72

Let's say that someone offered you the chance to invest for a return for 10% interest for your loan. Divide 72 by 10, and you get 7.2 which is the number of years it will take for you to double the value of your investment. If it's 5% interest it's 14.4 years.

What is the 8th miracle of the world? ›

Angkor Wat, located in Cambodia, is now considered the eighth Wonder of the World, beating Italy's Pompeii. The title of the eighth Wonder of the World is given to outstanding buildings or projects, and Angkor Wat has gained this recognition.

What is the meaning of the eighth wonder of the world? ›

Eighth Wonder of the World is an unofficial title sometimes given to new buildings, structures, projects, designs or even people that are deemed to be comparable to the seven Wonders of the World.

Why is compound interest called the 8th wonder of the world? ›

Seeing your money grow thanks to compound interest can be just as amazing as seeing the Great Wall of China or the Colosseum. He said, "Compound interest is the eighth wonder of the world. He who understands it, earns it; he who doesn't, pays it." That's a big deal, coming from a genius like Einstein!

What is the missing 8th wonder of the world? ›

The Amber Room, often referred to as the “Eighth Wonder of the World”, was one of Russia's most priceless works of art until it was looted by Nazi Germany and lost after the conclusion of WW II.

How much of the wonder is true? ›

Is The Wonder based on true events? The Wonder is an invented story, but what inspired it was the very real phenomenon of 'the fasting girl,' who claimed – or was said by others – to be able to live without food.

Is the Great Wall of China a Wonder of the world? ›

As one of the Eight Wonders in the world, the Great Wall of China has become the symbol of the Chinese nation and its culture. The Great Wall, one of the greatest wonders of the world, was enlisted in the World Heritage by UNESCO in 1987.

Is Niagara Falls a Wonder of the world? ›

Its massive display of water flow at Bridal Veil Falls, Horseshoe Falls, and American Falls with an average of 2,400,000 to 3,150,000 gallons of water falls per minute is enough to make it the 8th wonder of the world.

What is the 8th lost wonder of the world? ›

The greatest tourism and geoscience attraction in the southern hemisphere, in the nineteenth century were the siliceous Pink and White Terraces, the lost Eighth Wonder of the World in New Zealand. In 1886, the Mount Tarawera eruption buried the terraces.

What are the 8 wonders of the world? ›

The list includes the Great Wall of China, Petra, Christ the Redeemer, Machu Picchu, Chichen Itza, the Roman Colosseum, Taj Mahal, and Angkor Wat.

What is the 8th wonder of the world according to Einstein? ›

Compound interest is the eighth wonder of the world. He who understands it earns it … he who doesn't … pays it,” Albert Einstein famously said. If you earn compounding interest, you can become rich. But if you pay compounding interest, you will be in a debt spiral.

What is the monster in the Eighth Wonder of the World? ›

King Kong (1933)

What is the 8th wonder of the natural world? ›

Ngorongoro Crater – the world's eighth natural wonder.

What could be the 8th wonder? ›

Angkor Wat, one of the world's most famous temple complex in Cambodia, has another claim to fame now. It is now the Eighth Wonder of the World, beating other major giants, including Italy's famous Pompeii.

What is the 8th wonder of the universe? ›

It is the POWER OF COMPOUNDING which, according to the great Albert Einstein, is the 8th wonder of the world.

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