this paper with an empirical investigation into some of the risk factors and demographic variables that might explain these cross-sectional differences in portfolio composition. A number of previous studies have focused on the level and variability of wage income growth as one of the largest sources of undiversifiable income risk. Here we present evidence that, for the subset of the population that has significant stock holdings, income from entrepreneurial ventures (which we refer to as proprietary business income) represents a large source of undiversifiable risk that is more highly correlated with common stock returns. These findings motivate the investigation in the second part of the paper of a linear asset pricing model that incorporates proprietary income from privately held businesses as a risk factor.

This paper solves a realistically calibrated life-cycle model of consumption and portfolio choice with uninsurable labor income risk and borrowing constraints. Since labor income substitutes for riskless asset holdings the optimal share invested in equities is roughly decreasing over life. We compute a measure of the importance of non-tradable human capital for investment behavior to find that ignoring labor income generates large utility costs, while the cost of ignoring only its risk is an order of magnitude smaller. We also quantify the utility cost associated with typical heuristics advocated by financial advisors. The issue of portfolio choice over the life-cycle is encountered by every investor. Popular finance books (e.g. Malkiel, 1996) and financial counselors generally give the advice to shift the portfolio composition towards relatively safe assets, such as T-bills, and away from risky stocks as the investor grows older and reaches retirement. But what could be the economic

This paper surveys the field of asset pricing. The emphasis is on the interplay between theory and empirical work and on the trade-off between risk and return. Modern research seeks to understand the behavior of the stochastic discount factor ~SDF! that prices all assets in the economy. The behavior of the term structure of real interest rates restricts the conditional mean of the SDF, whereas patterns of risk premia restrict its conditional volatility and factor structure. Stylized facts about interest rates, aggregate stock prices, and cross-sectional patterns in stock returns have stimulated new research on optimal portfolio choice, intertemporal equilibrium models, and behavioral finance. This paper surveys the field of asset pricing. The emphasis is on the interplay between theory and empirical work. Theorists develop models with testable predictions; empirical researchers document “puzzles”—stylized facts that fail to fit established theories—and this stimulates the development of new theories. Such a process is part of the normal development of any science. Asset pricing, like the rest of economics, faces the special challenge that data are generated naturally rather than experimentally, and so researchers cannot control the quantity of data or the random shocks that affect the data. A particularly interesting characteristic of the asset pricing field is that these random shocks are also the subject matter of the theory. As Campbell, Lo, and MacKinlay ~1997, Chap. 1, p. 3! put it: What distinguishes financial economics is the central role that uncertainty plays in both financial theory and its empirical implementation. The starting point for every financial model is the uncertainty facing investors, and the substance of every financial model involves the impact of uncertainty on the behavior of investors and, ultimately, on mar-* Department of Economics, Harvard University, Cambridge, Massachusetts

Ongoing questions on the historical mean and standard deviation of the return on equities and bonds and on the equilibrium demand for these securities are addressed in the context of a stationary, overlapping-generations economy in which consumers are subject to a borrowing constraint. The key feature captured by the OLG economy is that the bulk of the future income of the young consumers is derived from their wages forthcoming in their middle age, while the bulk of the future income of the middle-aged consumers is derived from their savings in equity and bonds. The young would like to borrow and invest in equity but the borrowing constraint prevents them from doing so. The middle-aged choose to hold a diversified portfolio that includes positive holdings of bonds, and this explains the demand for bonds. Without the borrowing constraint, the young borrow and invest in equity, thereby decreasing the mean equity premium and increasing the rate of interest. I.

The paper studies the impact of the portfolio constraint imposed by the consumption demand for housing (the "housing constraint") on the household's optimal holdings of financial assets. Since the ratio of housing to net worth declines as the household accumulates wealth, the housing constraint induces a life-cycle pattern in the portfolio shares of stocks and bonds. For reasonable degrees of risk aversion, the changes in portfolio composition over the life-cycle can be dramatic. For example, for a coefficient of relative risk aversion of 3, the ratio of stocks to net worth in the optimal portfolio is .09 for the youngest households (ages 18-30) and .60 for the oldest (age 70 and over). Using data from the PSID on home values to construct household level panel data on the real after-tax return to owner-occupied housing, as well as data on the returns to financial assets, the paper estimates the vector of expected returns and the covariance matrix for the set of assets consis...

. I would like to thank the editor, John Heaton, and two anonymous referees for comments that greatly improved this paper. This paper is a substantially revised version of chapter 4 of my

In this paper, we analyze the relationship between age and portfolio structure for households in the United States. We focus on both the probability that households of different ages own particular portfolio assets and the fraction of their net worth allocated to each asset category.We distinguish between age and cohort effects using data from the repeated cross-sections of the Federal Reserve Board’s Surveys of Consumer Finances. We present two broad conclusions, First, there are important differences across asset classes in both the age-specific probabilities of asset ownership and in the portfolio shares of different assets at different ages. The notion that all assets can be treated as identical from the standpoint of analyzing household wealth accumulation is not supported by the data. Institutional factors, asset liquidity, and evolving investor tastes must be recognized in modeling asset demand. These factors could affect analyses of overall household saving as well as the composition of this saving. Second, there are evident differences in the asset ownership

We construct a life‐cycle model that delivers realistic behavior for both equity holdings and borrowings. The key model ingredient is a wedge between the cost of borrowing and the risk‐free investment return. Borrowing can either raise or lower equity demand, depending on the cost of borrowing. A borrowing rate equal to the expected return on equity — which we show roughly matches the data — minimizes the demand for equity. Alternative models with no borrowing or limited borrowing at the risk‐free rate cannot simultaneously fit empirical evidence on borrowing and equity holdings.

According to conventional wisdom, long-term bonds are appropriate for conservative long-term investors. This paper develops a model of optimal consumption and portfolio choice for infinite-lived investors with recursive utility who face stochastic interest rates, solves the model using an approximate analytical method, and evaluates conventional wisdom. As risk aversion increases, the myopic component of risky asset demand disappears but the intertemporal hedging component does not. Conservative investors hold assets to hedge the risk that real interest rates will decline. Long-term inflation-indexed bonds are most suitable for this purpose, but nominal bonds may also be used if inflation risk is low. (JEL G12)

Financial planners typically advise people to shift investments away from stocks and toward bonds as they age. The planners commonly justify this advice in three ways. They argue that stocks are less risky over a young person’s long investment horizon, that stocks are often necessary for young people to meet large financial obligations (like college tuition for their children), and that younger people have more years of labor income ahead with which to recover from the potential losses associated with stock ownership. This article uses economic reasoning to evaluate these three different justifications. It finds that the first two arguments do not make economic sense. The last argument is valid—but only for people with labor income that is relatively uncorrelated with stock returns. If a person’s labor income is highly correlated with stock returns, then that investor is better off shifting investments toward stocks over time. The views expressed herein are those of the authors and not necessarily those of the Federal Reserve Bank of Minneapolis or the Federal Reserve System. Most financial planners advise their clients to shift their investments away from stocks and toward bonds as they age.