This paper proposes to estimate the covariance matrix of stock returns by an optimally weighted average of two existing estimators: the sample covariance matrix and single-index covariance matrix. This method is generally known as shrinkage, and it is standard in decision theory and in empirical...

We derive an international asset pricing model that assumes local investors have preferences of the type "keeping up with the Joneses." In an international setting investors compare their current wealth with that of their peers who live in the same country. In the process of inferring the...

The goal of this paper is to estimate time-varying covariance matrices. Since the covariance matrix of financial returns is known to change through time and is an essential ingredient in risk measurement, portfolio selection, and tests of asset pricing models, this is a very important problem in...

The central message of this paper is that nobody should be using the sample covariance matrix for the purpose of portfolio optimization. It contains estimation error of the kind most likely to perturb a mean-variance optimizer. In its place, we suggest using the matrix obtained from the sample...

One plausible mechanism through which financial market shocks may propagate across countries is through the impact that past gains and losses may have on investors’ risk aversion and behavior. This paper presents a stylized model illustrating how heterogeneous changes in investors’ risk...

This paper shows how to introduce liquidity into the well known mean-variance framework of portfolio selection. Either by estimating mean-variance liquidity constrained frontiers or directly estimating optimal portfolios for alternative levels of risk aversion and preference for liquidity, we...

In this paper, we use a unique long-run dataset of regulatory constraints on capital account openness to explain stock market correlations. Since stock returns themselves are highly volatile, any examination of what drives correlations needs to focus on long runs of data. This is particularly...

We present a simple model of sovereign debt crises in which a country chooses its optimal mix of short and long-term debt contracts subject to standard contracting frictions: the country cannot commit to repay its debts nor to a specific path of future debt issues, and contracts cannot be made...

Contingent sovereign debt can create important welfare gains. Nonetheless, there is almost no issuance today. Using hand-collected archival data, we examine the first known case of large-scale use of state-contingent sovereign debt in history. Philip II of Spain entered into hundreds of...

In 2007, countries in the euro periphery were enjoying stable growth, low deficits, and low spreads. Then the financial crisis erupted and pushed them into deep recessions, raising their deficits and debt levels. By 2010, they were facing severe debt problems. Spreads increased and,...