The Long and the Short of Risk Parity
研究了风险平价在趋势跟踪、配对交易和因子投资三种多空策略中的应用，发现只有趋势跟踪在考虑交易成本后能可靠受益于风险平价。
The author investigates the application of risk parity (RP) to three types of systematic long–short investment strategies commonly used by practitioners: trend following, pairs trading, and factor investing. Although RP tends to improve risk-adjusted returns before transaction costs are considered, it increases portfolio turnover relative to simpler portfolio construction methods, such as equally weighted (EW) and naive risk parity (NRP) approaches. Whether an RP overlay can improve the after-cost, risk-adjusted performance of a long–short strategy depends strongly on the transaction costs involved and the level of correlation among the components of the strategy. Among the three long–short strategies studied, only trend following seems to reliably benefit from RP, especially when the correlations among the trends are higher, as in recent periods. Pairs trading, which is a high-turnover strategy with many largely uncorrelated bets, performs better with a simple EW approach. In factor investing, RP delivers risk-adjusted returns similar to an EW or NRP combination of 10 factors.