How does an equal-weighted index work and why does it need frequent rebalancing?

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AcadiFi · Accepted Answer

An equal-weighted index assigns each constituent the same weight at construction/rebalance. If there are N stocks, each has weight 1/N. The index return equals the simple average of constituent returns. Example: Five stocks have returns over the period of +12%, -4%, +8%, +22%, -6%. Equal-weighted return = (12 - 4 + 8 + 22 - 6)/5 = 6.4%. Compare to cap-weighted, which might show +10% because the large cap had the +22% return. Why frequent rebalancing is required: price drift quickly moves weights away from 1/N. If you start with $200 in each of 5 stocks ($1000 total), and one doubles while another halves, weights shift to 40%, 20%, 20%, 20%, 10% — no longer equal. Rebalancing sells winners and buys losers (the opposite of momentum). Rebalancing frequency trade-off: quarterly vs monthly — more frequent = tighter equal weighting but more transaction costs and taxes. S&P 500 Equal Weight (RSP ETF) rebalances quarterly. Characteristics: equal-weighted indices have a structural small-cap and value tilt because they systematically underweight mega-cap growth names and overweight smaller, cheaper ones. They tend to outperform cap-weighted over long rolling windows but with higher volatility and drawdowns in size-growth-led rallies.

How does an equal-weighted index work and why does it need frequent rebalancing?

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