In this article, we measure and interpret the common “factors” that describe money market returns. Results are presented for both three‐and four‐factor models. We find that the three‐factor model explains, on average, 86 percent of the total variation in most money market returns while the four‐factor model explains, on average, 90 percent of this variation. Using mimicking portfolios, we provide an interpretation of the systematic risks represented by these factors.

In this article, the authors measure and interpret the common 'factors' that describe money market returns. Results are presented for both three- and four-factor models. The authors find that the three-factor model explains, on average, 86 percent of the total variation in most money market returns while the four-factor model explains, on average, 90 percent of this variation. Using mimicking portfolios, they provide an interpretation of the systematic risks represented by these factors.

In models of trading with heterogeneous beliefs following Harrison‐Kreps, short selling is prohibited and agents face constant marginal costs‐of‐carry. The resale option guarantees that prices exceed buy‐and‐hold prices and the difference is identified as a bubble. We propose a model where risk‐neutral agents face asymmetric increasing marginal costs on long and short positions. Here, agents also value an option to delay, and a Hamilton‐Jacobi‐Bellman equation quantifies the influence of costs on prices. An unexpected decrease in shorting costs may deflate a bubble, linking financial innovations that facilitated shorting of mortgage‐backed securities to the collapse of prices.

We propose a model in which investors may choose to acquire costly information that identifies good assets and purchase these assets in opaque (OTC) markets. Uninformed investors access an asset pool that has been cream‐skimmed by informed investors. When the quality composition of assets for sale is fixed, there is too much information acquisition and the financial industry extracts excessive rents. In the presence of moral hazard in origination, the social value of information varies inversely with information acquisition. Low quality origination is associated with large rents in the financial sector. Equilibrium acquisition of information is generically inefficient.

We model the relationship between asset float (tradeable shares) and speculative bubbles. Investors with heterogeneous beliefs and short‐sales constraints trade a stock with limited float because of insider lockups. A bubble arises as price overweighs optimists' beliefs and investors anticipate the option to resell to those with even higher valuations. The bubble's size depends on float as investors anticipate an increase in float with lockup expirations and speculate over the degree of insider selling. Consistent with the internet experience, the bubble, turnover, and volatility decrease with float and prices drop on the lockup expiration date.

Asset prices contain information about the probability distribution of future states and the stochastic discounting of those states as used by investors. To better understand the challenge in distinguishing investors' beliefs from risk‐adjusted discounting, we use Perron–Frobenius Theory to isolate a positive martingale component of the stochastic discount factor process. This component recovers a probability measure that absorbs long‐term risk adjustments. When the martingale is not degenerate, surmising that this recovered probability captures investors' beliefs distorts inference about risk‐return tradeoffs. Stochastic discount factors in many structural models of asset prices have empirically relevant martingale components.

Many believe that compensation, misaligned from shareholders’ value due to managerial entrenchment, caused financial firms to take risks before the financial crisis of 2008. We argue that, even in a classical principal‐agent setting without entrenchment and with exogenous firm risk, riskier firms may offer higher total pay as compensation for the extra risk in equity stakes borne by risk‐averse managers. Using long lags of stock price risk to capture exogenous firm risk, we confirm our conjecture and show that riskier firms are also more productive and more likely to be held by institutional investors, who are most able to influence compensation.