What an interest rate really is
KnownMemorizeThe five building blocks of a rate
| Component | Pays you for |
|---|---|
| Real risk-free rate | Waiting |
| Inflation premium | Lost purchasing power |
| Default risk premium | The borrower might not pay |
| Liquidity premium | Selling quickly at a discount |
| Maturity premium | Long bonds swing more when rates move |
Memory hook Real + inflation = what a T-bill pays. Then the three risks, D, L, M: "Don't Lend Long".
Know it cold . A short government bill has no D, L or M premium.
Key terms
- opportunity cost Know the idea
- real risk-free interest rate Memorize
- inflation premium Memorize
- default risk premium Memorize
- liquidity premium Memorize
- maturity premium Memorize
- nominal risk-free interest rate Memorize
- Nominal risk-free rate Memorize what a short government bill pays
- Real risk-free rate the reward for waiting, with no inflation and no risk
- Inflation premium expected loss of purchasing power
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- Risk premiums Memorize all zero for a short government bill
- Default risk premium the borrower may not pay in full and on time
- Liquidity premium selling quickly costs you a discount
- Maturity premium long debt loses more value when rates rise
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Formulas
Quick example
Real risk-free 1.5%, inflation 3.0%, default 1.2%, liquidity 0.4%, maturity 0.6%. Yield ≈ 1.5 + 3.0 + 1.2 + 0.4 + 0.6 = 6.7%.
Quick example
Real 2.0%, inflation 3.0%. 1.02 × 1.03 − 1 = 5.06%, against 5.00% from the shortcut.
- 1.02×1.03−1= 0.0506, so 5.06%
- 1.02ENTER1.03×1− 0.0506
ENTER enter (on the HP, puts the number on the stack)