“If you move out of active management into passive, you have made an active decision, and for every day you stay using index management, that is another active decision,” Prugue says. The paper, “Beyond Cap Weight: The Search For An Efficient Beta”, which will be published for the first time in the Journal of Indexing January 2010 edition, aims to make investors think about their ‘passive’ or beta-generating equity portfolios like they do their alpha-seeking portfolios, which are routinely divided between value and growth, large and mid-cap and so on.
The vast majority of investors unquestioningly use a market cap-weighted portfolio for their passive beta strategy, however the paper tested what the outcomes would be if this cap-weighted strategy was blended with three other strategies for capturing equity market beta – “equal weighting”, “economic scale” (sometimes known as fundamental indexing or wealth-weighted indexing, depending on the benchmark provider), and minimum variance. The backtesting was done on the MSCI Developed Markets World Index, for the period January 1993 to June 2009.
The researchers found an optimal result was achieved by an even three-way split between cap-weighting, economic scale and minimum variance. They dubbed the blend “efficient beta”. The blend handsomely outperformed cap weighting for a lower volatility and better Sharpe Ratio over the 16-year backtest period. Prugue says the combination of the three produced a “negligible” bias towards value (a common criticism of fundamental indexing and minimum variance) and a similarly insignificant bias away from size.
Equal weighting was left out of the equation, because while it helped reduce “agency risk” by lowering the tracking error from the traditional capweighted approach, it greatly increased portfolio turnover. As it is, the “efficient beta” blend incurs a one-way portfolio turnover of 15.8 per cent via 12 annual rebalances, against 6.8 per cent and one annual rebalance for cap weighting. The researchers estimated an annual trading cost of 11 bps for “efficient beta”, versus 5 bps for cap weighting.