Financial Markets: Stocks, Bonds, Commodities, and Derivatives

Every economy has a problem to solve: some people have spare money they want to grow, and some people (companies, governments) need money to build things. Financial markets are the giant matchmaking machine that connects them. They move savings to where they can do the most work, put a price on the future, and let people swap risk they don't want for risk they do. This chapter takes you from "what is a share?" all the way to why a single hedge fund nearly broke the world economy in 1998.

Let's start by naming the four basic things that get traded.

Stock (also called equity or a share)

A small piece of ownership of a company. Own one share of Apple and you own a tiny slice of its future profits and assets. You may get to vote on big decisions, and if the company is wildly successful, your slice rises with no fixed limit. But if the company goes bankrupt, owners are paid last, after everyone else. The good news: the most you can lose is what you put in. That's limited liability — your house isn't on the hook for the company's debts.

Bond (also called fixed income or debt)

An IOU. You lend money to a government or company. In return they promise to pay you fixed interest (called the coupon) on a schedule, then return your original sum (the face value or par, usually $1,000) on a set date (maturity). A bondholder is a lender, not an owner — and lenders get paid before owners if things go wrong.

Commodity

A raw, physical good where one unit is interchangeable with any other — oil, gold, wheat, copper, coffee. The word for "interchangeable" is fungible: one barrel of crude oil is as good as the next. Most commodity trading is done on paper contracts, not by hauling actual barrels around.

Derivative

A contract whose value derives from something else (a stock, a bond, a commodity, an interest rate). It lets you trade the price exposure without owning the underlying thing. The two starter types are futures and options, which we'll unpack later.

Where securities are born vs. where they're traded

Here is a distinction almost everyone gets wrong. There are two markets, and the company only touches one of them.

The primary market is where a security is created and the issuer actually receives cash. For a stock, this is the IPO (Initial Public Offering) — the first time shares are sold to the public. For a bond, it's the original auction. This is the only moment the company or government gets money.

The secondary market is where those existing securities then trade between investors — the New York Stock Exchange, Nasdaq, and so on. When you buy a share of Apple today, your money goes to whoever sold it, not to Apple. Apple gets nothing.

So why does the secondary market matter at all? Because of liquidity — the ease of selling something quickly without crashing its price. Nobody would buy a stock at the IPO if they could never sell it again. The promise of an easy exit later is what makes people willing to invest now. A deep secondary market lowers the cost of raising money in the primary market. Liquidity is the quiet engine under everything.

What does a stock price actually represent?

In theory, a share is worth the value today of all the cash the company will ever hand to its owners in the future — dividends plus growth — shrunk down for two reasons: money later is worth less than money now, and the future is uncertain. In practice, the price is simply where the next buyer and the next seller agree, right this second. It's a constantly updated consensus guess about the future.

Multiply price by the number of shares and you get market capitalization ("market cap") — the market's total price tag on the company.

The iron law: risk and return

This is the spine of all investing. Higher expected return requires accepting higher risk. There is no investment that pays a lot, reliably, with no danger — if there were, everyone would pile in and the high return would vanish. Risk here means volatility: how wildly the value swings, including how badly it can fall.

Real long-run numbers make this concrete. From 1928 to 2025, the U.S. stock market (the S&P 500, with dividends reinvested) returned roughly 10% per year on average — about 6–7% after stripping out inflation. Over the same long span, safe 10-year U.S. government bonds (Treasuries) returned roughly 4.8%, and riskier corporate bonds in between.

The risk-free rate — the return on ultra-safe short-term government debt — is the anchor for everything else. When it moves, the whole system reprices. In 2020–21 it sat near 0%; by early 2026 the 10-year Treasury yield had climbed to roughly 4.3%. When safe assets suddenly pay more, investors demand more from risky ones too, and prices of stocks, houses, and bonds all adjust downward to compensate.

Diversification: the only free lunch

Economist Harry Markowitz called diversification "the only free lunch in finance." Here's why. Spread your money across investments that don't move together, and the losses in one can be offset by gains in another. You lower your total risk without giving up much expected return. That's rare and valuable.

Bonds: the inverse price–yield seesaw

This trips up nearly everyone, so go slowly. A bond's coupon is fixed in dollars. Say you own a $1,000 bond paying $50 a year (a 5% coupon). Now suppose market interest rates rise and brand-new bonds pay $70 a year. Who wants your stingy old $50 bond? Nobody — at full price. So its price falls until the $50 you collect, on a now-cheaper bond, works out to the same effective return as the new ones. The total return if you hold to the end is the yield to maturity (YTM).

        MARKET RATES RISE              MARKET RATES FALL
        ----------------              ----------------
   new bonds pay MORE            new bonds pay LESS
        |                              |
        v                              v
   old fixed-coupon bond          old fixed-coupon bond
   looks WORSE                    looks BETTER
        |                              |
        v                              v
   its PRICE  v  FALLS            its PRICE  ^  RISES
   so its YIELD ^ RISES           so its YIELD v FALLS

   RULE:  Bond price and yield ALWAYS move in OPPOSITE directions.

Plot the yields of bonds across different maturities and you get the yield curve. Normally it slopes upward: lock your money away longer, get paid more. But sometimes it inverts — short-term rates rise above long-term ones, meaning markets expect rates (and growth) to fall ahead. An inverted yield curve has preceded nearly every U.S. recession since the 1950s. It inverted again in 2022–23. It's a famous warning bell, though not a perfect one.

Derivatives: the double-edged sword

Now the dangerous, brilliant tools. Remember, a derivative gets its value from an underlying asset.

A future is a binding contract to buy or sell something at a set price on a set future date. It was invented for hedging — removing uncertainty. A wheat farmer in spring doesn't know what wheat will sell for at harvest, so he locks in today's price with a futures contract and sleeps easy. An airline locks in jet-fuel costs the same way. The risk of a price swing is transferred to someone willing to take it: a speculator, who bets on the price direction hoping to profit.

An option gives the right but not the obligation to buy (a call) or sell (a put) at a set strike price before it expires, in exchange for an upfront fee called the premium. If you buy an option, the most you can lose is that premium, while your upside can be large. The seller ("writer") pockets the premium but takes on the big risk.

The magic and the menace is leverage: a small deposit (the margin) controls a huge position. Leverage multiplies gains and losses alike. Used to transfer risk, it's healthy. Used to gamble, it's a time bomb.

How markets allocate capital — the social purpose

Step back. Beneath all the trading, financial markets perform a vital job for society: they steer savings toward their most productive uses. A company with bright prospects enjoys a high stock price and can borrow at a low yield — cheap money to grow. A weak company faces a low price and high borrowing costs. Prices act as signals, guiding capital toward winners and starving losers. Markets also provide price discovery (figuring out what things are worth), liquidity (easy exits), and risk transfer (moving risk to those best able to bear it).

Efficiency, bubbles, and an honest disagreement

Are prices "right"? The economics profession genuinely splits here. The Efficient Market Hypothesis (Eugene Fama) says prices already reflect all available information, so consistently beating the market is nearly impossible — which is the case for cheap index funds that just buy the whole market. The counter-view from behavioral finance (Robert Shiller) says humans herd, swinging between greed and fear, so bubbles and crashes are real and recurring. Tellingly, Fama and Shiller shared the 2013 Nobel Prize. The field hasn't settled it; respect both.

A bubble follows a familiar script: a gripping narrative → euphoria → leverage and fear-of-missing-out → "this time is different" → reality intrudes → crash.

The risk/return ladder

Here is the whole chapter in one picture. As you climb, both expected return and volatility rise together — you cannot get one without the other.

 RETURN &
 RISK
  ^                                    Leveraged DERIVATIVES
  |                                  (widest range of outcomes)
  |                            Speculative stocks / crypto
  |                       Commodities (oil, gold)
  |                  Small-cap & emerging-market stocks
  |             Blue-chip / index equities
  |        High-yield ("junk") bonds
  |     Investment-grade corporate bonds
  |   Government bonds
  | Treasury bills  <-- "risk-free" benchmark
  | Cash / savings
  +--------------------------------------------------> RISK
        (volatility rises as you climb the ladder)

Where you sit on this ladder is the single biggest decision in investing. Higher rungs reward patience over decades; lower rungs protect you when you can't afford a loss. The skill is matching the rung to your goal and your nerves.

Key Takeaways

• Stocks are ownership (paid last, unlimited upside); bonds are loans (paid first, fixed return); commodities are fungible raw goods; derivatives derive value from something else.
• Companies get cash only in the primary market (IPO/auction); the secondary market just trades existing securities — but its liquidity is what makes the primary market possible.
• A stock price reflects expectations about the future, not today's profits; higher expected return always demands higher risk — there is no free lunch except diversification across uncorrelated assets.
• Bond prices and yields always move in opposite directions; an inverted yield curve has flagged most U.S. recessions.
• Derivatives were built to reduce risk through hedging, but leverage makes them a double-edged sword — Barings, LTCM, and 2008 show how misuse spreads contagion.
• Markets allocate capital by turning prices into signals; they are mostly efficient yet periodically swept into bubbles, so invest with both discipline and humility.
• Always distinguish a derivative's huge "notional" face amount from the far smaller real money at risk.