Legendary investor Rob Arnott outlines the 2-part strategy that's helped his personal stock portfolio double the S&P 500 over 8 months

Tim Boyle/Bloomberg via Getty Images; BI

• Rob Arnott has used a leveraged long-short strategy to outperform the S&P 500 index since May.
• His approach leverages the differences between holdings in the RAUS ETF and the S&P 500.
• Arnott's method highlights inefficiencies in passive index funds.

Rob Arnott is revered in the investing world for his alternative passive index strategies, but when it comes to his own portfolio, the Research Affiliates founder...