Smart Beta, Alpha Decay, and Strategy Capacity in China and US Equities

Summary

This research summary compares factor-based Smart Beta products with active quantitative and index-enhancement strategies. It reports that applying commonly used Chinese equity alpha factors to S&P 500 constituents produced little excess return before fees, with valuation the only factor described as broadly effective and that effect weakening in recent years. Among the largest Smart Beta ETFs examined, half beat the S&P 500 over the prior decade; an equal-weight product led the comparison. The authors attribute product appeal to low fees, convenient trading, and moderate turnover.

For Chinese equities, the note examines how trading impact can erode higher-turnover alpha as assets grow. Using an I-STAR impact model, it finds that broader stock universes, more holdings, and less reliance on technical factors can improve capacity. It also constructs quality-oriented Smart Beta portfolios within the CSI 300 and CSI 500 universes and estimates a scale at which index enhancement and Smart Beta returns converge under stated rebalancing assumptions. These are historical findings and model estimates, with risks from model failure and extreme markets; they are not guarantees of future performance.

Key ideas

• The report frames Smart Beta and active quantitative returns as exposures to factor risk premia, with Smart Beta often using lower turnover.
• In its S&P 500 analysis, valuation was the only broadly effective tested alpha factor, and its effect weakened in recent years.
• The study uses an impact-cost model to assess how strategy capacity changes as capital grows.
• Broader universes, more holdings, and fewer technical factors were associated with better capacity for large Chinese equity strategies.
• The portfolio comparisons and capacity thresholds depend on historical data, model assumptions, and market conditions.

Tags

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.