My research field is asset pricing with a focus on return predictability, innovation and market efficiency, and delegated investment management. In Chapter 1, "Maximum Return Predictability", I develop two theoretical upper bounds on the R2 of the regression of stock returns on predictive variables. Empirically, I found that the predictive R2s are significantly larger than the upper bounds, implying that existing asset pricing models are incapable of explaining the degree of return predictability. For example, the predictive R2 of the price dividend ratio for the U.S. market forecasting is 0.27% with monthly data. However, the theoretical upper bound is at most 0.07% with respect to CAPM, Fama-French three-factor model, CARA, habitat-formation model, long-run risk model, or rare disaster model. The finding of this paper suggests the development of new asset pricing models with new state variables that are highly correlated with stock returns. Recently, several papers found that the predictive power of almost all the existing macroeconomic variables exists only during economic recessions but does not exist over economic expansions. There perhaps have two reasons. First, existing predictors are individual economic variables and cannot capture the dynamics of the whole market. Second, the recognized predictive regression does not distinguish the varying ability of macro variables in forecasting the financial market. In Chapter 2, "Economic and Market Conditions: Two State Variables that Predict the Stock Market," Guofu Zhou and I identify two new predictors that capture the state of the economy and the state of the market condition, and found that the forecast of the market risk premium by the two predictors outperform a pooled forecast of dozens of existing predictors. Moreover, they forecast the stock market not only during down turns of the economy, but also during the up turns when other predictors fail. In decentralized investment management, there is always a friction between the principal and the manager. In Chapter 3, "The Servant of Two Masters: A Common Agency Explanation for Side-by-Side Management," I present a common agency model to study side-by-side (SBS) management in which a manager simultaneously manages two funds and separately contracts with the two different fund principals. The contracting is decentralized and includes two types of externalities: the manager's efforts are substitutable and the performance in one fund can generate a spillover effect on the other fund. The two principals can choose competition or free-riding. Under public contracting, competition is more likely to dominate free-riding. Under private contracting, however, free-riding becomes more important. In either case, SBS could generate better performance than standalone management.