One is that these returns are calculated on a time-weighted, rather than asset-weighted basis.

FORBES: Chasing the Mirage of Hedge Fund Returns

The SPIVA Scorecard provides performance comparisons corrected for survivorship bias, equal- and asset-weighted peer averages and measures of style consistency for actively managed U.S. equity, international equity and fixed income mutual funds.

FORBES: Active Funds Continue to Struggle

So Lack performs his own asset-weighted calculations (similar to the internal rate of return methodology of measuring private equity or real estate fund performance) using BarclayHedge data to measure how the average investor as distinct from the average fund has done.

FORBES: Chasing the Mirage of Hedge Fund Returns