The Invesco S&P 500 Low Volatility ETF (NYSEARCA:SPLV) is a well-established fund that aims to offer investors the upside of the U.S. equity market with a smoother return profile. The traditional thinking would be that more risk equals higher returns, as would follow from the efficient markets hypothesis. If risk is priced correctly, then shouldering more of it should offer greater gains in compensation. But there may be a low-volatility anomaly. Historically, there has been some evidence that higher volati ...