Mean-variance investing is all about diversification. Diversification considers assets holistically and exploits the interaction of assets with each other, rather than viewing assets in isolation. Holding a diversified portfolio allows investors to increase expected returns while reducing risks....

After taking into account biases induced by infrequent trading and selection, it is unlikely that illiquid asset classes have higher risk-adjusted returns than traditional liquid stock and bond markets. On the other hand, there are significant illiquidity premiums within asset classes. Portfolio...

Municipal (muni) bonds are risky and trade in illiquid markets, and both effects serve to raise muni yields relative to Treasuries. On the other hand, the tax exemption of muni bonds tends to lower their yields. We decompose the muni yield spread into credit, liquidity, and tax components....

About once a quarter. We compute optimal tactical asset allocation (TAA) policies over equities and bonds when both asset returns are predictable. By varying how often the weights are reset, we estimate the benefits and costs of different frequencies of TAA decisions. Tactical tilts taking...

American university and college endowments now hold close to one-third of their portfolios in private equity and hedge funds. We estimate the implied beliefs of endowments about alternative assets' returns relative to equities and bonds. At the end of 2012, the typical endowment believes that...