Preface

Almost everything written about indices treats them as either a number or a product. There are books that argue for passive investing as a strategy. There are trading manuals on futures and options that happen to use an index as their underlying. There are methodology papers written by index providers for other index providers. What is difficult to find is the connected account: the one that begins with a rule someone wrote down about which companies qualify and ends with the cost of the contract sitting in your account, treating everything in between as one subject rather than several unrelated ones.

That is the gap this book was written to close. It covers what an index actually is, a calculated number rather than an asset you can hold, and the eligibility rules that decide which companies enter it: market-capitalisation thresholds, liquidity minimums, domicile requirements, and financialhealth criteria. It covers how the number is built, through market-capitalisation, price, equal, and fundamental weighting, and how the divisor keeps it continuous when constituents change. It covers how it is maintained through corporate actions, reconstitutions, committee discretion, and the mechanical trading that published rules make predictable. It covers how the number is transmitted into something you can actually hold, through futures, options, ETFs, contracts for difference, and traditional index funds, and what each of those costs in spread, roll, financing, dividends forgone, and tax. And it covers what moves the number at all: constituent earnings, valuation multiples, interest rates, central-bank policy, sentiment, and the business cycle. The aim is breadth held together by logic rather than depth in one corner. There is no chapter here on the internal mathematics of a single thematic index, and none that argues one participation approach is correct for everyone. Those books exist and they are worth reading once you understand where they sit. What this book gives you is the whole architecture at once.

It is a manual rather than a story. It does not build towards a revelation and it does not have to be read in the order it is printed. Every heading is written to stand on its own, so you can open the book at the section on float adjustment, or at the section on overnight gap risk, and find something complete rather than something that assumes you were present for the previous sixty pages. Where a section genuinely depends on an idea developed elsewhere, it names the chapter, so you always know where to go and never have to guess whether you have missed something.

Two conventions run through the text, and both exist to keep you reading rather than searching.

The first is that every industry term is defined in square brackets the moment it first appears, immediately after the word itself. In Chapter 1 the sentence reads: Sector concentration [the percentage of an index represented by a single industry] determines how sensitive an index is to sector-specific shocks. The definition sits inside the sentence that first needs it, so nothing is used before it has been explained. Every term defined this way reappears in the Key Terms list at the end of its chapter and again in the Glossary at the back, which means a term you half-remember from a hundred pages earlier is always recoverable in seconds.

The second is that specific claims, outside figures, and reasoning that did not originate here carry a small number in square brackets. Chapter 1 states that approximately 90 per cent of active US large-cap managers underperform the S&P 500 over 15-year periods [25]. That bracketed 25 refers to the twenty-fifth entry under Chapter 1 in the Notes at the back of the book, where the source is named in full. Where a figure is checkable, the number tells you where to check it. Where a claim belongs to someone else, the number tells you whose it is. You are never asked to take a number on trust.

The chapters are ordered by what each idea requires, not by convention about where a book on markets ought to begin. You are not shown the cost of rolling a futures contract before you have been shown that an index is a calculated figure and cannot be owned directly. You are not shown how the divisor absorbs a corporate action before you have been shown the formula the divisor sits inside. You are not shown a margin call before you have been shown what notional value is and how a contract multiplier converts index points into money. The sequence runs: what an index is and what its construction rules do to it, then how it is calculated and kept continuous through change, then how you reach it and through which instrument, then the mechanics of opening, holding, and closing a position on it, then what the result actually is once costs and tax are taken out, and finally the forces that move the number and what a defensible role in these markets looks like. Nothing is assumed before it has been built.

If you have never looked past the headline figure, begin at the first page of Chapter 1 and take the chapters in order. Nothing is assumed of you beyond attention. If you already follow indices closely, you will find your own entry point, and it is usually not where you expect. Someone who has held an index fund for a decade may never have read why an ordinary share split moves the Dow’s divisor but leaves the S&P 500’s untouched. Someone who trades index futures may never have worked through the fact that the quarterly contracts settle against a Special Opening Quotation rather than the closing value everyone watches. Someone who tracks constituent changes may never have seen how far the index effect has collapsed since the 1990s. The book was built so that all of these readers can use the same pages.

The practical instruction is simple. Read it once from beginning to end, including the parts that look familiar, because the sequence is doing work that the individual sections cannot do alone. Then stop treating it as a book and start treating it as a reference. Keep it where you can reach it, and return to the heading you need when the market puts a question in front of you. It was written to be opened repeatedly, not admired once.