Dividend yield measures the annual dividend income from a share relative to its current market price. It is calculated as annual dividend per share divided by share price and is usually expressed as a percentage. The purpose is to provide an income-based return metric that allows investors to compare shares, funds, or sectors on a like-for-like basis in terms of dividend income generated per unit of price paid. This is particularly relevant for income-focused investors assessing whether a share offers attractive income relative to alternatives, while recognising that dividend yield is not the same as total return because it excludes capital gains or losses. Option A relates more to retention and reinvestment, which is assessed using payout ratios and earnings coverage rather than dividend yield alone. Option B is tax-planning related and not the core purpose of the metric. Option D is not what dividend yield measures; a high yield can reflect a falling share price or expectations of dividend cuts as well as growth. The key exam point is comparability of dividend income return.