Price Return Index

A price return index is built by aggregating constituent prices under a chosen weighting scheme, then dividing by a divisor. In a price-weighted index the numerator is the simple sum of share prices; in a market-capitalisation-weighted index it is the sum of price multiplied by shares outstanding, often adjusted for free float. The divisor exists solely to preserve continuity: when a constituent is replaced, a stock splits, or shares are issued, the divisor is reset so the index level does not jump on an event that carries no economic information.

The return itself is the ending index level minus the beginning level, divided by the beginning level. Nothing in that expression makes room for cash paid out to shareholders. When a stock trades ex-dividend, its price mechanically falls by roughly the distribution, the index level falls with it, and the cash simply disappears from the measurement.

Total return equals price return plus income return, and for equities the income component is the dividend yield. The annual wedge looks modest, but it is not additive over time: each year's distributions, if reinvested, buy shares that themselves appreciate and distribute. Compounding turns a persistent yield gap into a wide divergence in terminal index levels over decades.

The size of the wedge is regime-dependent and market-dependent. Broad developed-market yields have generally been lower in recent decades than in the mid-twentieth century, while markets dominated by mature, cash-generative sectors, such as parts of Europe and the United Kingdom, carry structurally higher payout ratios than growth-heavy indexes. Emerging market and small-cap indexes sit at different points again. Any cross-market performance comparison drawn from price indexes therefore embeds a bias toward the low-yield market.

Headline quotes, derivatives and benchmarking each use a different convention. The levels reported for the S&P 500, FTSE 100 and Nikkei 225 are price return series, and listed index futures and options generally settle against those price levels, with expected dividends instead entering the futures price through the cost-of-carry relationship. Germany's DAX is the well-known exception: the flagship performance index reinvests distributions, and a separate price index is published alongside it, so German equity performance quoted against non-German price indexes looks flattered unless the series are matched.

Investment mandates and manager evaluation almost always specify total return benchmarks, because a fund that receives dividends in cash must be compared against an index that does the same. Tracking-error and information-ratio calculations measured against a price index would credit the manager with the entire dividend stream as apparent alpha.

Be fluent in three operations. First, compute a single-period index return from beginning and ending levels, then decompose it into price and income components when the dividend yield is supplied. Second, rebuild an index level after a corporate action by adjusting the divisor so the pre-event and post-event levels coincide. Third, identify which weighting method the question implies, since price weighting, cap weighting and equal weighting produce different index returns from identical constituent price moves.

Judgement questions test whether the correct series has been selected: total return for performance attribution, manager evaluation and long-horizon wealth comparisons; price return when the discussion concerns market levels, valuation multiples applied to the index, or the settlement basis of an index derivative. Stating the reason for the choice matters as much as the arithmetic.