Risk parity is a buzzword in pension finance right now. Ray Dalio of Bridgewater popularized the concept and he has become one of the biggest names in the institutional investment community. His strategy is simple: 1) Don't try and predict the future. 2) Allocate your capital across different asset classes that respond differently to different economic environments so that you have a neutral portfolio.
This should sound familiar because it is exactly what the Permanent Portfolio does. The risk parity guys complicate things by weighting assets inversely to their volatility (which changes over time), but the principles are the same. After all gold, stocks, and LTT all have roughly equivalent volatility so the equal split with the PP's weightings is no coincidence. It is essentially a risk parity strategy.
AQR and Invesco have launched a couple of funds within the last few years, and I think it will be very interesting to watch their performance vs. the PP over time. Although they are guided by essentially the same framework as the PP, their execution of the philosophy is much more complicated (and expensive).