The world's largest asset class — larger than global equities. From overnight money markets to 30-year government bonds to complex structured credit. How it works, how it's priced, and what role it plays in a serious portfolio.
Nine chapters covering the full fixed income spectrum — from overnight lending to structured products to portfolio construction.
Fixed income is any financial instrument where the issuer (borrower) promises the holder (lender) a defined schedule of payments — typically periodic interest (the "coupon") plus return of principal at maturity. You are the bank.
The "fixed" in fixed income can be misleading — many instruments pay floating rates. The defining characteristic is the contractual obligation: unlike equity holders, fixed income investors do not share in corporate upside. In return, they have legal priority over equity in the capital structure. In bad years with no profits, bondholders get paid before shareholders receive anything.
Fixed income spans an enormous time horizon — from overnight interbank lending to 100-year bonds issued by Austria and Mexico. The key dividing line between money markets (short-term) and bond markets (long-term) is approximately one year to maturity.
| Instrument | Typical Maturity | Issuer | Key Feature | Where Covered |
|---|---|---|---|---|
| Overnight / Fed Funds | 1 day | Banks | Central bank policy rate anchor | § Money Markets |
| Treasury Bills (T-Bills) | 4–52 weeks | Governments | Issued at discount; no coupon | § Money Markets |
| Commercial Paper (CP) | 1–270 days | Corporations | Short-term unsecured corporate funding | § Money Markets |
| Certificates of Deposit | 1 month–5 years | Banks | Fixed-term bank deposit, negotiable | § Money Markets |
| Repurchase Agreements (Repo) | Overnight–months | Banks / institutions | Collateralised short-term borrowing | § Money Markets |
| Government Bonds (Gilts / Treasuries) | 2–30+ years | Sovereign governments | The risk-free benchmark; semi-annual coupon | § Bonds |
| Investment-Grade Corporate Bonds | 3–30 years | Corporations (BBB– and above) | Spread over government; covenants | § Bonds / Credit |
| High Yield ("Junk") Bonds | 5–10 years | Corporations (below BBB–) | High spread; equity-like risk | § Exotic Bonds |
| Inflation-Linked Bonds (TIPS) | 5–30 years | Governments | Principal adjusts with CPI | § Exotic Bonds |
| Asset-Backed Securities (ABS / MBS) | Variable | SPV (mortgages, auto loans, etc.) | Cash flows from underlying pool | § Exotic Bonds |
| Convertible Bonds | 5–10 years | Corporations | Debt + embedded equity option | § Exotic Bonds |
| Interest Rate Swaps | 1–30 years | OTC bilateral | Exchange fixed for floating cashflows | § Derivatives |
The global bond market exceeds $130 trillion — roughly 1.5× global GDP. The US Treasury market alone is ~$27 trillion, making it the single most important financial market in the world. Treasury yields serve as the global "risk-free rate" — the baseline against which all other asset returns are measured. When the Federal Reserve changes its policy rate, it ripples through every fixed income instrument on earth within minutes.
The short-term end of the fixed income spectrum. Maturities under one year, near-cash liquidity, and the plumbing through which central bank policy flows into the real economy.
Issued by national governments at a discount to face value — the investor pays less than £100 and receives £100 at maturity, with the difference representing the return. No periodic coupon. The most liquid and safest money market instrument globally.
Sold by auction: governments announce the amount on offer, investors bid at various discount rates, and the cut-off yield determines who receives bills. In the UK, the Debt Management Office (DMO) runs weekly auctions. In the US, the Fed auctions T-Bills weekly — with minimum purchases of just $100, accessible to all. A bid-to-cover ratio above 2.5× signals strong demand.
LIBOR (London Interbank Offered Rate) was the daily benchmark rate at which banks lent to each other, published across 10 currencies and 15 maturities. It underpinned over $300 trillion of financial contracts globally — mortgages, student loans, corporate facilities, derivatives.
LIBOR was discontinued in 2023 after the rate-rigging scandal revealed that it was based on bank submissions rather than actual transactions, making it manipulable. Its replacement, SOFR (Secured Overnight Financing Rate), is based on actual overnight repo transactions — approximately $1 trillion daily — making it transaction-based and manipulation-resistant. The transition is one of the most consequential structural reforms in fixed income history.
A repo is simultaneously a sale and a forward purchase. Party A sells securities (typically government bonds) to Party B and agrees to repurchase them at a higher price on a specified future date. The price difference is the implicit interest rate — the "repo rate."
Why it matters: Repos are the lubricant of the financial system. Banks fund their bond inventories through repos. Central banks conduct open market operations via repos to set short-term interest rates. In 2019, dysfunction in the US repo market caused overnight rates to spike to 10% — exposing how fragile system-wide liquidity can be. A "haircut" is applied to collateral: if bonds are pledged as collateral, the cash received may be only 95-98% of market value, providing a buffer against price moves.
Commercial Paper (CP) is short-term unsecured debt issued by large corporations — effectively an IOU. Companies use it to fund operating expenses, manage cash flow, and bridge between longer-term financing. The 270-day US limit reflects the SEC registration threshold. CP requires no collateral, so only highly rated issuers can access the market.
The 2008 crisis revealed CP's fragility: when Lehman Brothers collapsed, the Reserve Primary Fund "broke the buck" (NAV fell below $1) due to CP holdings, triggering a systemic run on money market funds. The Fed was forced to backstop the entire market. Money market funds — which aggregate small investor capital into diversified CP/T-bill portfolios — are the primary vehicle through which retail investors access money markets.
Central banks (the Fed, Bank of England, ECB) control short-term rates through the rate they pay on reserves and the rate they charge for emergency lending. Every rate change transmits immediately into the money market — affecting every mortgage, corporate loan facility, and money market fund return globally. Understanding the money market is understanding how monetary policy actually operates.
Long-term debt instruments — typically one year to 30+ years — where the borrower pays regular interest (coupons) and returns principal at maturity. The price, yield, and risk characteristics of these instruments form the backbone of all financial markets.
A UK government "gilt" named Treasury 4.5% 2034 means: the government borrowed £100 nominal (face value) per bond, pays £4.50 per year (split into two semi-annual payments of £2.25), and repays the full £100 nominal in 2034. If you buy this bond in the secondary market at £108 (above par), you still receive £4.50/year and £100 at maturity — the extra £8 premium you paid represents a built-in capital loss over the life of the bond. This affects your actual yield to maturity.
| Term | Definition | Practical Significance |
|---|---|---|
| Face Value / Nominal | The principal amount returned at maturity — typically £100 or $1,000 | This is NOT what you pay in the secondary market; actual market price varies with interest rates |
| Coupon Rate | Annual interest as % of face value — fixed at issuance for most bonds | A 5% coupon on £100 nominal = £5/year regardless of market price fluctuations |
| Current (Flat) Yield | Annual coupon / Market price × 100 | Tells you your income return as % of what you paid — ignores capital gain/loss to maturity |
| Yield to Maturity (YTM) | IRR of all future cash flows (coupons + principal) at current price | The true all-in return if held to maturity — the number that matters most |
| Par / Above Par / Below Par | Price = 100 (par), >100 (premium), <100 (discount) | Bonds issued at par often trade at premium/discount as rates change after issuance |
| Clean Price | Price excluding accrued interest since last coupon date | The price quoted in newspapers / Bloomberg — not what you actually pay |
| Dirty Price | Clean price + accrued interest — what you actually pay | The settlement price; buyer compensates seller for days of accrued coupon |
| Redemption Date | Date principal is repaid and the bond ceases to exist | Some bonds are callable (issuer can repay early) — complicating YTM calculations |
UK government bonds (gilts) are sold by the Debt Management Office and traded in an OTC market. The name "gilt-edged" reflects their historically strong credit — the UK has never defaulted on domestic-currency debt. Conventionals pay semi-annual coupons; index-linked gilts (linkers) adjust both coupon and principal for RPI inflation. Short gilts (under 7 years), medium (7–15 years), and longs (15+ years) trade in distinct markets with different investor bases.
Treasury Bills (under 1 year), Notes (2–10 years), and Bonds (10–30 years) form the deepest, most liquid bond market in the world. The 10-year Treasury yield is the global benchmark — the reference rate against which all other borrowing costs are measured. Traded OTC in a $27 trillion market with average daily volumes exceeding $600 billion. TIPS (Treasury Inflation-Protected Securities) link principal to CPI — a critical tool for real return investors.
German government bonds — Schätze (2yr), Bobls (5yr), and Bunds (10yr+) — are the Eurozone's risk-free benchmark. In periods of stress, capital flows into Bunds drive yields negative (investors pay for the privilege of safety). The spread between Bunds and Italian BTPs or Greek bonds is a real-time measure of eurozone sovereign risk. Bund yields anchoring near zero post-2015 forced European institutional investors into riskier assets — reshaping the entire continent's investment landscape.
Corporate bonds function like government bonds but carry credit risk — the company might default. This is compensated by the credit spread: the extra yield over the equivalent government bond. A BBB-rated 10-year bond yielding 5.5% when the 10-year Treasury yields 4.0% has a 150bp spread. Covenants (legally binding restrictions on the issuer) protect bondholders: negative covenants restrict what management can do (take on more debt, sell key assets); positive covenants require actions (maintain certain financial ratios, provide audited accounts).
The most important concept in all of fixed income — and the one most commonly misunderstood by beginners. Master this, and everything else follows.
When market interest rates rise, existing bond prices must fall — to make their fixed coupons competitive. When rates fall, existing bond prices rise. This is not a theory; it is an arithmetic certainty.
David Swensen notes that even a senior New York Times financial journalist once wrote that rising interest rates cause bond prices to increase. The relationship is "perfectly perverse prose" — counterintuitive enough that even sophisticated writers get it backward. If you understand only one thing about fixed income, it is this inversion.
Duration measures how much a bond's price will change for a given change in yield. It is expressed in years (representing the weighted average time to receive cash flows) but used as a sensitivity measure. A bond with duration of 7 will fall approximately 7% in price if yields rise 1% (100 basis points).
Longer-dated bonds have higher duration and therefore greater price sensitivity to yield changes.
A zero-coupon bond has duration equal to its maturity — all cash flow comes at the end. Adding coupons reduces duration as earlier cash flows "pull" the weighted average earlier. This is why pension funds, which have very long-dated liabilities, prefer long-duration bonds — the asset and liability move together when rates change.
Duration assumes a linear relationship between yield changes and price changes — a useful approximation. Convexity captures the fact that the relationship is actually curved: when yields rise significantly, prices fall less than duration predicts; when yields fall significantly, prices rise more. Positive convexity is a free option — it works in the investor's favour in both directions of large yield moves. Investors pay for convexity through lower yields on convex bonds.
Two dimensions determine a bond's yield: the creditworthiness of the issuer (credit risk) and the time until repayment (interest rate risk). Together they build the entire fixed income pricing universe.
Rating agencies (S&P, Moody's, Fitch) assess the probability of default and express it as a letter grade. The critical dividing line is BBB– / Baa3 — the border between investment grade and high yield ("junk"). Many institutional investors are prohibited by mandate from holding bonds below this threshold, creating powerful forced-selling dynamics at downgrades.
Mortgage-backed securities (MBS) containing thousands of US subprime mortgages were routinely rated AAA by S&P, Moody's, and Fitch. The underlying assets were far riskier than the models assumed — particularly their correlation in default. When house prices fell nationally (an event the models treated as nearly impossible), AAA-rated tranches suffered catastrophic losses. Ratings are a starting point for analysis, never a substitute for it. The agencies are paid by issuers — a structural conflict that has never been fully resolved.
The yield curve plots the yield on government bonds of the same credit quality but different maturities — from overnight to 30 years. Its shape contains information about market expectations of future interest rates, growth, and inflation.
Three explanations coexist. Expectations theory: long rates reflect expected future short rates — if the market expects rates to rise, long bonds must yield more today. Liquidity premium theory: investors demand extra return for tying capital up longer and bearing greater interest rate risk. Market segmentation theory: different investor bases (banks in short end, insurers/pension funds in long end) operate independently, creating natural demand patterns that shape each segment.
When 2-year Treasury yields exceed 10-year yields, the curve is inverted. This has preceded every US recession since 1955. The mechanism: banks borrow short and lend long — inversion makes this unprofitable, tightening lending conditions. The 2022–2023 inversion was the deepest in 40 years, with 2-year yields 100bp+ above 10-year. Whether it retains its predictive power as central bank intervention increases is actively debated.
Beyond plain-vanilla government and corporate bonds lies a rich universe of structures designed for specific investor needs, issuer constraints, and market conditions.
The principal of a TIPS (Treasury Inflation-Protected Security) adjusts daily with CPI. A 2% coupon on an inflation-adjusted principal that grows with inflation delivers a real return above inflation — unlike conventional bonds whose fixed payments are eroded in real terms.
Swensen classifies TIPS as a real asset, not a fixed income instrument — because their value tracks inflation, not nominal rates. In a diversified endowment portfolio, TIPS serve as purchasing power insurance, particularly valuable during unexpected inflation spikes. The "breakeven rate" (TIPS yield vs nominal Treasury yield) reveals market inflation expectations — a closely watched signal.
Bonds rated below BBB– (investment grade). Coined "junk" by critics but now a $2T+ asset class. Issuers are companies that cannot access investment-grade markets — leveraged buyouts, early-stage companies, turnarounds, and cyclicals.
High-yield bonds sit between investment-grade credit and equity in the risk/return spectrum. Returns are driven partly by interest income (coupon of 6–12%+) and partly by credit risk — default rates average 3–5% per year historically, spiking to 10–15% in recessions. The asset class was pioneered by Michael Milken at Drexel Burnham in the 1980s — he correctly identified that diversified portfolios of junk bonds offered risk-adjusted returns superior to investment-grade bonds, even accounting for defaults.
A bond with an embedded equity option — the holder can convert into shares at a predetermined conversion price. This equity optionality allows issuers to pay a lower coupon than a straight bond (the option has value). Investors accept lower yield in exchange for equity upside if the company succeeds.
Classic use case: Amazon and AOL issued convertibles in the late 1990s at 5–6% — roughly half what they'd have paid on straight bonds. The conversion option was the attraction. In accounting, convertibles create complexity: they dilute EPS when converted and require bifurcated treatment of the debt and equity components. For investors, they offer asymmetric payoff — bond-like downside protection with equity-like upside.
Not a reference to the euro currency — Eurobonds predate it by decades. A Eurobond is simply a bond issued outside the jurisdiction of the currency in which it is denominated. The first Eurobond was a $15 million issue by Autostrade (Italian motorway company) in Luxembourg in 1963.
Structural advantages: no withholding tax on interest (paid gross), less regulation than domestic markets, anonymity for investors, and access to global pools of capital in any currency. The Eurobond market now exceeds $25 trillion. Key variant: the Medium-Term Note (MTN) programme — a standing legal structure allowing a corporation to issue bonds in multiple currencies, maturities, and structures over many years under a single prospectus.
Securitisation transforms pools of illiquid receivables (mortgages, auto loans, credit card balances, student loans — even Bowie's royalties and Arsenal's ticket receipts) into tradeable bonds. A Special Purpose Vehicle (SPV) buys the assets, issues bonds backed by those cash flows, and the risk is "tranched" — senior tranches receive first and are safest; junior tranches absorb losses first and yield more.
The 2008 crisis was fundamentally a failure of MBS tranching assumptions: models assumed US house prices could not fall nationally, and that mortgages in different states were largely uncorrelated in default. Both were wrong. The AAA tranches of subprime MBS suffered losses that history said were near-impossible. The lesson: the complexity of the structure should never obscure the quality of the underlying asset.
Sharia law prohibits riba (interest), making conventional bonds impermissible for observant Muslim investors. Sukuk replaces interest with asset-backed rental income or profit-sharing. The SPV structure issues certificates entitling holders to a share of real asset income — functionally equivalent to a bond return but structured as a participation in asset ownership and its profits.
The market has grown from its 1975 origins to over $2 trillion globally. Malaysia and the Gulf states (UAE, Saudi, Bahrain) dominate issuance. Governments — including the UK, which issued its first sovereign sukuk in 2014 — have used sukuk to access the deep pool of capital from Islamic sovereign wealth funds and institutional investors. For family offices in the GCC context, understanding sukuk is non-optional.
Derivatives don't fund borrowing — they redistribute risk. They allow corporates to fix their borrowing costs, investors to express yield curve views, and banks to hedge enormous interest rate exposures without moving actual bond portfolios.
An interest rate swap is an agreement to exchange a series of fixed cash payments for floating-rate payments (or vice versa) on a notional principal — without ever exchanging the principal itself. The notional is simply the reference amount for calculating payments. The global IRS market exceeds $400 trillion in notional outstanding.
Both want to borrow £150M for 8 years. Cat prefers fixed; Dog prefers floating. By swapping, both achieve their preferred exposure at a lower combined cost than if each borrowed directly in their preferred market.
Result: Cat pays 50bp less than borrowing fixed directly. Dog pays less than borrowing floating directly. The swap exploits the fact that the interest-rate risk premium differs between fixed and floating markets for each borrower — a form of comparative advantage.
A company borrows £80M at LIBOR+200bp (floating), but its board prohibits additional floating-rate exposure. The treasurer calls a bank's swap desk, receives a fixed rate quote of say 4.8%, and enters a swap: company pays 4.8% fixed, receives LIBOR. Net result: company pays LIBOR+200bp to lender, receives LIBOR from swap desk, pays 4.8% to swap desk. All-in fixed cost: 4.8%+200bp = 6.8%. The floating exposure is eliminated. A swaption is an option on a future swap — paying a premium today for the right (but not obligation) to enter a swap at a predetermined fixed rate.
A CDS is a bilateral contract where the protection buyer pays a periodic premium (the "spread," in basis points) and the protection seller agrees to pay face value if a "credit event" (default, restructuring, bankruptcy) occurs on the reference entity's debt. The CDS market reached $62 trillion notional in 2007.
AIG's financial products division sold $440 billion of CDS on MBS tranches — collecting premiums without posting adequate collateral. When MBS prices fell, counterparties demanded collateral calls. AIG could not pay. The US government had to inject $182 billion to prevent a collapse that would have triggered simultaneous defaults across every major bank that had bought protection from AIG. CDS had concentrated systemic risk, not distributed it. The lesson: the seller of protection must hold capital commensurate with the risk assumed.
Bond futures are exchange-traded contracts to buy or sell a standardised bond at a set price on a future date. The most important are 10-year Treasury Note futures (CME) and Bund futures (Eurex) — among the most liquid contracts in the world. Unlike physical bond purchases, futures require only a margin deposit (typically 2–5% of notional), providing natural leverage.
Portfolio managers use them to rapidly adjust duration without trading physical bonds — increasing/decreasing interest rate sensitivity in minutes. CTAs (trend-following hedge funds) trade bond futures as their primary vehicle for expressing rates views. Corporations use them to hedge future debt issuance — locking in today's rates before a bond deal.
Bond futures settle against a notional "benchmark" bond, but the seller can choose which eligible bond to deliver — naturally choosing the "cheapest-to-deliver" (CTD). The CTD bond's price dominates the futures price. Understanding which bond is CTD and how it might change as rates move is essential for institutional futures users — basis trading exploits mispricings between the futures and CTD bond.
Interest rate options give the buyer the right (but not obligation) to borrow or lend at a specified rate, providing asymmetric protection against adverse rate moves.
Series of call options on a floating rate. A company borrowing at LIBOR+200bp buys a cap at 5% — if LIBOR rises above 5%, the cap pays the difference. Provides a maximum all-in cost ceiling while retaining the benefit if rates fall. Premium paid upfront.
Series of put options — establishes a minimum rate. A bank with floating-rate assets (mortgages) buys a floor to protect income if rates fall below a threshold. Selling a floor to partially fund a cap creates a collar — a popular zero-cost hedging structure.
Option to enter a swap at a predetermined fixed rate on a future date. A payer swaption gives the right to pay fixed (useful if rates may rise). A receiver swaption gives the right to receive fixed (useful if rates may fall). Widely used by corporate treasurers pre-planning large bond issuance.
Fixed income is not simply "the safe bit." It plays multiple distinct roles — and understanding which role you are asking bonds to fill determines what type of bonds you should own.
In equity market crises, investors engage in "flight to quality" — selling risky assets and buying government bonds. In October 1987 (−20% equities in a day), during the 1998 Russia/LTCM crisis, during 2008, and during March 2020 — Treasuries and gilts rallied as equities collapsed. This negative correlation with equities is the key diversification benefit.
Swensen's verdict: Treasury bonds provide unique diversifying power but modest expected returns. Allocations should be modest for long-term investors — primarily serving as crisis insurance rather than return generation. A 5–15% allocation is typical in institutional portfolios.
Swensen classifies TIPS as a real asset, not a fixed income instrument — placing them alongside real estate, oil, and timber as inflation hedges. The principal adjusts daily with CPI, providing a guaranteed real (after-inflation) return. In a period of unexpectedly high inflation, TIPS significantly outperform conventional bonds.
Portfolio role: Complement rather than substitute for nominal bonds. An investor concerned about both equity market crashes (needing nominal Treasuries) AND inflation surprises (needing TIPS) should hold both — they protect against different risks.
Investment-grade corporate bonds pay a spread over government bonds, compensating for default risk. High-yield bonds pay significantly more — but their behaviour in equity market crises resembles equities (spreads widen, prices fall alongside stocks). They do not provide the ballast that government bonds do.
The Swensen warning: Many investors hold corporate bonds believing they are "safe" while earning extra yield. In a crisis, spread widening can cause investment-grade portfolios to fall 10–15% even as they avoid default. The correlation with equities — the asset they are supposed to diversify — increases precisely when diversification matters most.
Pension funds and insurance companies have long-dated, fixed liabilities — promised payments to pensioners decades into the future. These liabilities behave like long-duration bonds: their present value rises when interest rates fall. A pension fund that holds equities while rates fall could find its liabilities growing faster than its assets — creating a deficit even without any investment loss.
Liability-driven investing (LDI) matches asset duration to liability duration using long-dated bonds and interest rate swaps. The 2022 UK LDI crisis occurred when rapid rate rises caused leveraged LDI strategies to face collateral calls simultaneously — forcing gilt sales that further pushed rates higher in a dangerous spiral, ultimately requiring Bank of England intervention.
Swensen's framework from Module 2 applies directly: government bond markets (Treasuries, gilts, Bunds) are highly efficient — active management after fees rarely adds value. Passive index funds or ETFs are appropriate. Corporate and high-yield bonds, emerging market debt, and structured credit are less efficient — active managers with genuine credit analysis skill can add value by identifying mispriced risk. The problem: identifying those managers in advance is as difficult here as anywhere else in markets.
Three tiers of depth. Start with Tier 1 for narrative context and conceptual grounding. Tier 2 builds analytical rigour. Tier 3 is practitioner-level for those managing or evaluating fixed income portfolios seriously.