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Foreign hi, I'm Andy Tempte, and welcome to the Saturday Morning Muse. Start your weekend with musings that are designed to improve financial literacy around the world. Today is September 13, 2025. Over the past two weeks, we've been exploring one of the most powerful forces in finance, compound interest and compounding. We began with Benjamin Franklin's 200 year experiment and the mathematical foundations laid by scholars like Edmond Halley. Last week, we discovered the simple math behind compounding and saw how redirecting a daily five dollar latte habit into the S&P 500 could create nearly $1 million of wealth over a 40 year care. There's a darker side to this story. The same mathematical force that can make you wealthy can also destroy your financial future. Today, we're exploring compound interest's evil twin, compound debt. Now let's take you back to last week and our compound interest formula. Here, future value equals the current principal value times one plus the interest rate raised to to the number of years or the number of periods. Note that there's an exponent in this formula. And so compounding and exponential math, they go together. And this formula doesn't care whether you're the investor earning the returns or the borrower paying interest. The mathematics work exactly the same way, with one crucial difference. When you're investing, compound interest builds wealth for you. When you're borrowing, especially at high interest rates, compound interest builds wealth for your lenders, but it destroys yours. Now, every month you carry a credit card balance. You're not just paying interest on your original purchases, you're paying interest on the interest from previous periods, when minimum payments don't cover the full interest charges for that month, which creates the same snowball effect that we celebrated last week, except now that snowball is rolling downhill toward you. So today we're primarily going to be talking about the credit card trap. So we revisit our latte example from last week, but with a twist. Instead of investing that daily $5, imagine that you're charging it to a credit and then only making minimum payments on that credit card debt. So suppose that you put $5 daily, which is our latte money, on that credit card, with a 22% annual interest rate, which is roughly the current average for credit cards. Credit cards use daily compounding, just like we did last week, meaning that interest is calculated and added to your balance every single day. If you make typical minim minimum payments of about $50 monthly, here's what happens. After five years of charging lattes and making those payments, you'd owe approximately $11,200. You charged $9,125 worth of lattes over that five year period. But compound interest added over $2,000 in additional debt despite your payments. Because you were paying and the minimum wasn't keeping up with the interest expense. After 10 years, your debt would explode to nearly $44,600. Even though you only charged $18,250 worth of coffee, the compound interest has grown to more than double your actual spending. At this payment rate, you would never pay off the debt. The minimum payments wouldn't even interest charges and your balance would grow indefinitely. So this is the trap that you can get yourself into if you only make minimum payments and those minimum payments don't keep up with interest charges. Unfortunately, this is the financial reality in millions of American households. According to recent Federal Reserve data, the average American household carries credit card debt of over $6,000. With many household households owing much more. Let's consider another scenario. Someone who accumulates $10,000 in credit card debt at 22% interest. If they make monthly payments of $300, which would be above the minimum payment, it will take them over four years to pay off this debt. And they'll pay approximately $5,600 in interest. With these more substantial payments on your credit card that did exceed the minimum requirements and they did reduce the principal balance each month, that $10,000 in purchases actually cost $15,600. The opportunity cost of creating debt versus investing makes this even more painful. What if that same $300 were invested monthly in the S&P 500 over that same four year period? Well, it would grow to approximately $17,600. And that's assuming the S&P 500's long term historical average of 10%. Later on, in future episodes, we'll show that that 10% isn't guaranteed every year. And you could actually lose money over a four year period. But over run, you're going to earn roughly 10% on the S and P. So by carrying credit card debt instead of investing, this person just didn't lose $5,600 in interest payments. They lose the entire future value of what that $300 per month could have become if it were invested versus if it were spent on a high interest credit card. Now, the cruel irony is that credit card interest rates are typically two to three times higher than long term investment returns. While the stock market has historically returned about 10% annually, credit cards commonly charge 18 to 25% interest or more. This creates a mathematical impossibility you cannot invest your way out of high interest debt. No reasonable investment strategy can consistently earn 22% annually to offset credit card based interest rates. The math simply doesn't math. Even worse, credit card companies structure minimum payments to keep you trapped in this cycle. Minimum payments barely cover interest charges even if they do, meaning that your principal balance decreases painfully slowly and can actually increase over time. Credit card companies make billions of dollars in profit from this compound interest trap. Now, understanding compound interest's dark side reveals why financial advisors nearly universally recommend paying off high interest debt before investing every dollar that you use to pay down a 22% interest credit card balance gives you an immediate 22% return by eliminating that interest charge. Show me an interest an investment that guarantees 22% annual returns without risk. Well, you can't because they don't exist. So paying off high credit card debt is one of the best investments that anyone can make. This is why the standard advice is this. Build a small emergency fund first. Then aggressively pay off all high interest credit card debt. Then begin serious investing. Fighting compound interest with compound interest doesn't work when the debt interest rates are higher than investment returns. So what's the solution? The solution isn't to fear compounding or compound interests it to respect its power and ensure it works for you and not against you. So here's the framework. First, avoid high interest rate debt whenever possible. Credit cards should be tools of convenience, not financing vehicles. If you can't pay cash for something, you probably can't afford it. Second, if you already carry high interest rate debt, attacking it becomes your highest return investment. Paying off a 22% credit card debt guarantees a 22% return on every dollar applied to the balance. And third, once you're free of that high interest rate debt, then redirect every dollar that was going to debt payments toward investing. So over these three episodes, we've seen compound interest from really every angle. Ben Franklin's patient 200 year experiment showed us its historical power. Our latte example demonstrated compound interest's wealth building potential. And today's credit card scenario reveals its destructive capability. The fundamental lesson is compound interest is neither good nor evil. It's a mathematical force that amplifies whatever financial decisions you make. Make good decisions and it becomes your greatest ally in building wealth. Make poor decisions and it becomes a relentless enemy that can destroy your financial future. Remember that our series on financial literacy began with numerous episodes on the power of good decision making. At its core, financial literacy is rooted in making better decisions every day. For now, remember every financial decision you make is either working with compound interest or against it. Choose wisely. Until next week, I wish you grace, dignity and compassion. My name is Andy Tempte. This is the Saturday Morning Muse. You can find the show on all the major streaming services as well as out on YouTube. Please like, subscribe, rate and most importantly, share this public good with your friends, your neighbors, your colleagues, and maybe a family member or two. The show is produced by Nicholas Tempte. We'll see you next time on the Saturday Morning Museum.