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The offbeat personal finance blog for responsible people.

Compound Interest Isn’t Everyone’s Best Friend

By Len Penzo

compound interestInvest $100 that earns a 6% annual return and you’ll have $106 a year later. The uninitiated might expect to see $112 in their account after two, but they’d actually have $112.36 because interest not only accrued on the original principal of $100, but also on the $6 gained in year-one. Left untouched, that account would balloon to $1842 after 50 years — 18 times the original stake! No wonder Albert Einstein called compound interest “the most powerful force in the universe.”

The bottom line: Unfortunately, compound interest is a double-edged sword. It makes dedicated investors very wealthy … and irresponsible borrowers extremely poor.

Photo Credit: NASA Goddard Space Flight Center

November 17, 2022

Comments

  1. 1

    The Griper says

    that same principle applies to inflation also, doesn’t it?

    • 2

      Len Penzo says

      One word: you bet it does! (oops … apparently, inflation affects words too) 😉

  2. 3

    Freeat33 says

    @The Griper. You are right. ( As I see it ) I was not an economist. I was a cocaine addict who became a Plumber! How I always hear it is when parents think they are expert investors because they paid $6k for their house and today it is worth so much more.
    In 1974 Inflation ( Usually 2-3% recently ) hit 11.03%, then in 1975, 9.2% then 5.75%, 6.5%, 7.62%. 11.22%. 13.58%. 10.35% and 6.16% in 1982. In those nine years a $6K home would have increased to $13K. Hero investor? Nope. Just using inflation in the right way. The dangerous way would have been to someone who owed that same 6K. Ouch! Now imagine that the U.S. Debt in 1977 was $708 Billion. I would have liked to explain how inflation worked more, but I only know it is bad and to use it to my advantage. Just as I don’t need to understand how gravity works to push heavy things down hills.

  3. 4

    Cherleen says

    Obviously, saving on compounded interest is not advantageous if you will be putting a small amount on the account. However, if you will set aside $1000 at the same interest rate, that will be $1191 in 3 years. You will be making the money 47 years earlier that you would have made in 50 years. I hope I made any sense. 🙂

  4. 5

    Money Beagle says

    Very true, not to mention that most interest is now calculated daily, so your interest charges get bigger every day between payments and you pay a little interest on the interest even over the course of a month.

  5. 6

    Amanda L Grossman says

    So true! I am happy to be on the beneficial side of the sword…

    By the way, it was lovely meeting you and your wife. She seems so down to earth and fun!

    • 7

      Len Penzo says

      It was a pleasure meeting you too, Amanda! Yeah, the Honeybee is extremely fun; she’s a real people person. (Lucky for me.) 🙂

  6. 8

    Jason says

    You’re exactly right. I’d much rather pay off a 15% credit card than I would invest in the market hoping to earn 6%.

  7. 9

    Chris says

    Yes, but that $1842 in 2072 is only worth $465 in today’s world. Still an increase in overall worth, but definitely not as large. Just used an inflation calculator referenced below to back calculate what $ value = $1842 in 2072.

    • 10

      Len Penzo says

      Yes, inflation diminishes the returns in terms of purchasing power. But that’s the folly of fiat currencies not backed by a gold standard — and a subject for another post. 🙂

      Did that assume an annual 2% inflation rate? I suspect the rate will be much higher than that in the coming years, assuming our debt-based monetary system survives that long. (Hint: It won’t.)

  8. 11

    Jimmy says

    or you can work your whole life and save up $900,000 and then the stock market will crash (like it did in 2008) and you will be left with $200,000! That’s what happens when you let someone else control your savings… America wants the “herd” to invest in the stock market … or should I say the extremely rich, the ones who influence the media, want the average joe to invest in the stock market and keep promising compounded interest … until they mess it all up … again … as they seem to be doing right now!

  9. 12

    Lance says

    People in debt need to realize this kills them! You normally only hear about the good side though which stinks for those in debt.

  10. 13

    Oscar says

    Of course, when interest rates are at still relatively low levels (and practically zero between 2008 and 2021) … compound interest has been nobody’s friend.

  11. 14

    mc says

    I’d bet at least a few years of compound interest that Einstein never said or wrote anything about compound interest, or anything regarding finances for that matter, whatsoever. It’s just one of those things that someone probably just made up in the 80s and now it is a commonplace.

    Your Friendly Stickler for Quote Sourcing of the day,
    mc

    • 15

      Len Penzo says

      Party pooper. 😉

      But fortunately for me, absence of evidence is not evidence of absence!

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