Albert Einstein once called compound interest the ‘eighth wonder of the world.’ Those who understand it earn it; those who do not, pay it. Understanding how compounding works is the single most important concept in long-term investing.
What is Compound Interest?
Simple interest is paid only on the principal amount. Compound interest is interest earned on interest. Over time, your money begins to snowball, growing at an accelerating rate because you earn returns not just on your initial capital, but also on the gains generated in previous years.
The Power of Time
The most important variable in the compound interest formula is time, not the interest rate itself. Starting to save just 10 years earlier can result in double or triple the total retirement balance. That is why young professionals should start investing immediately, even if it is only a small amount each month.
An Illustrative Example
If you invest $500 a month starting at age 25, assuming an average annual return of 8%, you will accumulate over $1.5 million by age 65. However, if you wait until age 35 to start, you will end up with just $675,000—less than half as much, despite only missing out on 10 years of contributions!
Be Consistent and Patient
The first few years of compounding are not very impressive. It looks like a slow crawl. But after two or three decades, the curve turns sharply upward. Staying the course during market downturns is key to letting compounding work its incredible wealth-building magic.