It wasn't so long ago that we had different asset classes that we could use in designing a portfolio. Asset allocation did little, if anything, to protect from market declines, but you could use different combinations to tweak the risk vs. return of portfolios. For example, you used to be able to add bonds to a portfolio to reduce risk, while also reducing returns. Adding Gold or commodities used to also change the risk/return structure of portfolios. You also used to be able to add international and emerging market stocks to increase returns and risk. Now adding any of these assets just adds risk and reduces return. This creates a problem for the asset allocator, when US stocks are the only game in town what do you do? Do you keep fixed exposure to the other asset classes and just ride them down? Do you have 100% stocks and hope that we don't have another bear market? This new paradigm may just reverse itself, but if it doesn't asset allocators are going to have to think long and hard about new ideas in portfolio design.