🏦 Bonds & The Fed · Lesson 4 of 7 · 8 min
Credit Ratings — What AAA Actually Means
📊 On the morning Lehman Brothers went bankrupt, its bonds were still rated investment-grade. In 2008, mortgage bonds packed with loans that were never going to be repaid carried AAA — the same grade as the US government. Ratings are opinions in very confident lettering. Here's what they actually mean, and what they miss.
💡 Key idea
AAA to BBB = investment grade. BB and below = junk/high-yield. Ratings are opinions, not guarantees.
🧠 Why it matters
Rating agencies (Moody's, S&P, Fitch) grade bonds by default risk. AAA = highest safety. BBB and above = investment grade. BB and below = 'junk' (high yield). Riskier borrowers must offer higher yields to attract lenders — but the extra yield is no guarantee you'll be made whole.
🌍 In the real world
💥 In 2008, Lehman Brothers' bonds were still rated investment grade on the morning it filed for bankruptcy — Moody's had merely put them 'on review' five days earlier. The ratings were wrong. Now you know why sophisticated investors don't just read the rating — they read the balance sheet.
📌 Takeaways
- AAA = safest, lowest yield
- Junk bonds = high yield, high default risk
- Rating agencies can be late or wrong
📖 Terms in this lesson
Credit rating: A grade (AAA to junk) for how likely a borrower is to pay its bonds back.
✅ Test yourself
What does a 'AAA' bond rating mean?
- Highest risk
- Highest safety — lowest chance of default
- Only available to governments
- Triple the interest rate
Answer: B · Highest safety — lowest chance of default
AAA is the highest rating — given to borrowers considered extremely unlikely to default. Only a couple of US companies (Microsoft, Johnson & Johnson) hold it; even the US government was cut one notch below AAA by all three agencies (S&P 2011, Fitch 2023, Moody's 2025), though Treasuries remain the market's safety benchmark.
What are 'junk bonds'?
- Fraudulent bonds
- Bonds rated BB or below — high yield, higher default risk
- Bonds from junk companies only
- Old expired bonds
Answer: B · Bonds rated BB or below — high yield, higher default risk
Junk bonds (also called high-yield bonds) are rated below investment grade. They pay more interest precisely because they carry more risk.
Why don't ratings guarantee safety?
- They do — AAA is always safe
- Rating agencies can be wrong, slow, or conflicted
- Governments ban accurate ratings
- Only stock ratings matter
Answer: B · Rating agencies can be wrong, slow, or conflicted
The 2008 crisis showed rating agencies gave AAA to toxic debt. Ratings are a starting point, not a guarantee — always look at the underlying fundamentals.
Quiz, XP and streaks in the app. No sign-up needed.