Excess return index

Some indices track only price movement measured against a yardstick. Others track price movement plus any income earned along the way — dividends, interest, or in commodities, the gain from rolling futures forward.

The first kind is an excess return index: how much better (or worse) did the investment do than a benchmark, stripped of any income component. It answers a narrower question than a total return index does.

The workbook's definition: excess return indices, also known as excess return or total return above a benchmark, measure performance relative to a specified benchmark or risk-free rate, focusing solely on the return generated in excess of that benchmark, without considering any income generated by the assets. This contrasts with a total return index, which captures both price change and income.

Indian commodity indices built from futures prices are generally total return indices, because rolling an expiring near-month contract into the next month generates a return component of its own — the difference between the expiring and new contract prices. The workbook's own illustration: an index fund manager rolling a Bullion Index Futures position from a near-month contract at Rs 16,000 to a next-month contract at Rs 16,100, when the one-month carry cost is only Rs 50, generates a roll cost that is more than covered if the next-month contract subsequently rises further in a persisting contango market — the "excess" return over and above what carrying cost alone would predict.

A wholesale bullion dealer holding physical gold stock takes a short position in bullion index futures as a hedge. Because the dealer is short, it benefits from the same roll dynamic that costs a long index investor money: selling the near-month contract and buying the cheaper-relative next-month contract before expiry.

Suppose the dealer's short position rolls 50 contracts from a near-month sale at Rs 91,200 per 10 grams to a next-month purchase at Rs 91,500 — a Rs 300 roll cost per contract that a long holder would absorb. As the short, the dealer instead earns this Rs 300 per contract, on top of any gain or loss from the metal's own price move, precisely because it is capturing the "excess" income embedded in a contango-shaped futures curve rather than merely tracking the spot price.

Chapter 2, section 2.5, under "Uses of Index Futures," works through the excess return concept using the Bullion Index Futures roll example, distinguishing it from a total return index. Expect a question distinguishing excess return from total return, and one testing that Indian commodity indices built on futures prices are, in general, total return indices — even though a wholesaler can specifically position to capture the excess-return component through a short index roll.

• Excess return ignores income; total return includes it. Reversing the two definitions is the most common error.
• Indian commodity futures-based indices are classified as total return indices, not excess return indices, even though the workbook uses an "excess return" strategy example built on top of one — the strategy and the index classification are two different things.
• The roll gain only shows up in a persisting contango market. In backwardation, rolling into the next month can be a cost rather than a gain for a long position, and a benefit for a short one — the direction flips with the shape of the curve.