Financial Instruments: Stocks, Bonds, Derivatives, and Cash

Markets trade a bewildering variety of things, but almost all of it sorts into four categories: stocks (equities), bonds (fixed income), derivatives, and cash equivalents. The fastest way to keep them straight is not to memorize a risk/return table but to ask each one the same question: what claim does this piece of paper actually give you, and against whom? The four classes answer differently, and every risk/return property they have grows out of that answer.

Stocks: the residual claim

A share of stock is fractional ownership in a company. Buy one and you own a piece of the business — whatever is left after every debt is paid belongs to the owners, in proportion to their shares. That’s a residual claim: you get paid after every creditor, but there is no ceiling on what “whatever is left” can be worth.

Companies issue stock to raise capital for growth, acquisitions, or operations, and the money goes to the company itself (that’s a primary-market event). Investors buy it for capital appreciation (the price goes up) and dividends (regular cash payouts) — neither of which is guaranteed. The “no ceiling” half of the residual claim is why stocks carry higher expected returns than bonds over long periods; the “paid last” half is why they’re more volatile and can lose you money. These aren’t two separate properties. They’re two sides of the same coin.

There’s a layer within equity, too. Common stock carries voting rights, with dividends at the company’s discretion. Preferred stock pays a fixed dividend, carries no vote, and sits ahead of common in the payout order — which makes it, in character, half a step toward being a bond.

Three numbers come up constantly when looking at a stock: the P/E ratio (price-to-earnings), market capitalization (price × shares outstanding), and dividend yield (annual dividend ÷ stock price).

Bonds: a creditor’s fixed schedule

A bond is a loan you make to a government or a corporation. They pay you interest on schedule (the coupons) and return your principal at maturity. You’re the mirror image of the shareholder: a creditor, paid before the owners, but with your payments written into the contract — however well the business does, all you get is the coupon.

Issuers like bonds because they’re usually cheaper than bank loans and the terms are flexible; governments issue them to finance deficits, companies to finance growth. Investors buy them for a steady income stream, lower risk than stocks, and the diversification benefit of holding them alongside equities.

“Safer,” though, is not “safe.” When interest rates rise, existing bonds fall in price — that’s interest rate risk — and issuers do sometimes fail to pay. Hence the three numbers that matter for a bond: yield to maturity (total return if held to maturity), duration (price sensitivity to rate changes), and credit rating (a rough gauge of default risk). Running the common types from lower risk to higher: government bonds (T-bills, T-notes, T-bonds by maturity), investment-grade corporates, then high-yield bonds — known more bluntly as junk. The US also has municipal bonds, whose usual selling point is tax exemption.

Derivatives: contracts about prices

The first two instruments both have a real borrower or business behind them. A derivative does not — it’s a contract whose value is derived entirely from the price of some underlying asset, which is where the name comes from. Your counterparty isn’t a company raising money; it’s whoever took the other side of the contract.

Four basic forms: a forward is a private agreement to buy or sell at a set price on a future date; a future is a forward moved onto an exchange and standardized; an option is the right — not the obligation — to buy (call) or sell (put) at a set price; a swap is an exchange of cash flows, with interest rate swaps the most common. People use them for three things: hedging risk they already have, speculating on price direction with leverage, and arbitraging price differences.

Option Payoffs by Position

For an option with strike K, premium P, and underlying price S_T at expiration, the four basic option positions each have a distinct payoff profile. Long and short are mirror images of each other, what one gains, the other loses, and only the underlying price determines who wins and who loses.

The asymmetric profiles are why options are useful both for limiting downside (long options) and for collecting premium income with defined risk (short options). Always identify which side of the trade you are on before thinking about “directional risk.”

Which corrects a popular half-truth worth flagging: “options have limited downside and unlimited upside” is true only for the buyer. The table says it plainly — the seller’s position is the exact opposite, a capped premium collected against a potentially large tail loss. An option’s asymmetry depends entirely on whether you are long or short, and leverage amplifies gains and losses on both sides without prejudice.

One more thing to fix in your head: derivatives are a zero-sum game. For every buyer there’s a seller, and in cash-flow terms every dollar one side gains, the other side loses. The market works anyway because hedgers are willing to “lose” a little in expectation to buy certainty — a trade that leaves both sides better off in utility, if not in cash.

Cash and cash equivalents: a claim on nothing but liquidity

Cash equivalents are highly liquid, low-risk instruments that convert back to money on short notice: physical currency and demand deposits (checking accounts), money market funds (backed by short-term government securities), Treasury bills (government paper under one year), and certificates of deposit (CDs).

Their job in a portfolio isn’t to earn — it’s to wait and to cushion: a parking place for capital awaiting deployment, a liquidity buffer for emergencies, and the baseline against which every other investment gets measured. The price of that service is equally explicit: the lowest risk of the four classes, the lowest expected return, and a negative real return whenever inflation runs — your purchasing power quietly shrinks.

Putting them together

The four classes divide the labor:

How much you put in each — the asset allocation — is the most important investment decision you make. Studies show asset allocation explains 90%+ of a portfolio’s return variability over time. Note what that claim measures: the variability of returns, not their level.

The principle behind the mix is the core observation of modern portfolio theory: combining assets that don’t move perfectly together reduces portfolio risk without sacrificing expected return. That is the power of diversification. As for the optimal proportions, there is no universal answer — expected return, volatility, the correlations between assets, your liquidity needs, your time horizon, and your tax situation all sit in the equation.

References

• Bodie, Kane, Marcus, Investments. McGraw-Hill, 2020. ISBN: 978-1-26-057101-6.
• Fabozzi, Foundations of Financial Markets and Institutions. Pearson, 2014. ISBN: 978-0-13-299456-6.