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The framework: it's a rate comparison
At its core this is one question: does your money do more good paying down a debt, or invested? And that comes down to comparing two percentages — the interest rate on the debt versus the return you could reasonably expect from investing.
Paying off a loan charging 22% is a guaranteed, tax-free 22% return — you stop losing 22%. Investing might earn more, but it's uncertain. So the comparison is really "guaranteed X% vs. probable Y%."
Two things to do before either
1. Build a small emergency buffer first. Even $1,000 keeps a surprise expense from becoming new credit-card debt and undoing your progress. Around 37% of U.S. adults couldn't cover a $400 emergency with cash (Federal Reserve — SHED 2023), which is exactly how debt cycles start.
2. Capture the full employer 401(k) match. If your employer matches contributions, that's free money — often a 50% or 100% instant return on what you put in (U.S. Department of Labor — What You Should Know About Your Retirement Plan). No debt payoff and no investment beats a guaranteed double, so always contribute at least enough to get the full match.
Then split by the interest rate
After the buffer and the match, sort your debt by rate:
- High-interest debt (roughly 8%+ — credit cards, payday loans, many personal loans): pay this off aggressively before investing more. Credit cards commonly run over 20% APR (Federal Reserve — Consumer Credit, G.19). Almost no investment reliably beats that, and the payoff is risk-free.
- Low-interest debt (roughly under ~5–6% — many mortgages, some student loans, 0% promo financing): here, investing for the long term has historically earned more than the interest you'd save. The U.S. stock market has returned roughly 10% annually on average over the long run (about 6–7% after inflation) (SEC / Investor.gov — compound interest & long-term investing). Paying the minimum and investing the rest is defensible.
- The middle (~6–8%): a judgment call. Splitting the difference — some to debt, some to investing — is reasonable, and the guaranteed return of debt payoff is worth weighting toward.
Don't ignore the psychology
The math says attack the highest rate first (the "avalanche"). But if quick wins keep you motivated, paying the smallest balance first (the "snowball") can work better for you — and the strategy you actually stick with beats the optimal one you abandon.
The short version
Emergency buffer → full employer match → high-interest debt → then the toss-up between low-interest debt and investing. Run your own numbers, but when in doubt, guaranteed beats probable, and 20% debt beats almost everything.
