Research
Portfolios for long-term investors
Jan 13 2022. Review of Finance 2021 This is an essay on portfolios, based on a keynote talk at the NBER conference, ``New Developments in Long-Term Asset Management” Jan 21 2021. Read the paper. Slides for the talk
Jan 13 2022. Review of Finance, 26(1), 1-42 (2022). This is an essay on portfolio theory and practice, which evolved from a keynote talk at the NBER conference, ``New Developments in Long-Term Asset Management” Jan 21 2021. Portfolio practice looks almost nothing like portfolio theory. I offer two ideas: look at the stream of payouts or dividends directly, and ask what the function of asset markets is, and what your role in them is. The average investor holds the market portfolio. How are you different? A lot of fascinating asset pricing hasn’t yet made its way into portfolio theory, and I think about how to do that. Complete the model, and add interesting heterogeneity.
Read the paper (free access link to published version)
doi link. Last Manuscript (but the free access link should work)
The Dog and the Straw Man
The Dog and the Straw Man: Response to “Dividend Growth Does Not Help Predict Returns Compared To Likelihood-Based Tests: An Anatomy of the Dog”. Click title for longer summary
The Dog and the Straw Man: Response to “Dividend Growth Does Not Help Predict Returns Compared to Likelihood-Based Tests: An Anatomy of the Dog.” 2021. Critical Finance Review 10(3), 465-470. published version. Response to Erik Hjalmarsson and Tamás Kiss. Their paper is a critique of my “Dog that did not Bark: A Defense of Return Predictability” I respond to the critique.
Rethinking Production Under Uncertainty
Published (advance access) Review of Asset Pricing Studies July 2020. I investigate a representation of technology in which producers can transform output across states of nature. This representation lets us write down a complete production-based asset pricing model, in which the discount factor equals marginal rates of transformation.
Published (advance access) Review of Asset Pricing Studies July 2020. I investigate a representation of technology in which producers can transform output across states of nature. This representation lets us write down a complete production-based asset pricing model, in which the discount factor equals marginal rates of transformation.
The Fama Portfolio
2017. University of Chicago Press. Edited with Toby Moskowitz. Collection of Gene Fama papers, with introductions by myself, Toby, Ken French, Bill Schwert, René Stulz, Cliff Asness, John Liew, Ray Ball, Dennis Carlton, Cam Harvey, Lan Liu, Amit Seru and Amir Sufi. The introductions explain why the papers are so important and how we think about the issues today. My essays are here, other essays may be on other authors' webpages. For everything else you'll have to buy the book or e book. My essays (most joint with Toby):
Preface;
Efficient Markets and Empirical Finance;
Luck vs. Skill;
Risk and Return;
Return Forecasts and Time Varying Risk Premiums;
Our Colleague.
2017. University of Chicago Press. Edited with Toby Moskowitz. Collection of Gene Fama papers, with introductions by myself, Toby, Ken French, Bill Schwert, René Stulz, Cliff Asness, John Liew, Ray Ball, Dennis Carlton, Cam Harvey, Lan Liu, Amit Seru and Amir Sufi. The introductions explain why the papers are so important and how we think about the issues today. My essays are here, other essays may be on other authors' webpages. For everything else you'll have to buy the book or e book. My essays (most joint with Toby):
Preface;
Efficient Markets and Empirical Finance;
Luck vs. Skill;
Risk and Return;
Return Forecasts and Time Varying Risk Premiums;
Our Colleague.
Macro-Finance
2017. Review of Finance 21(3): 945-985. Links: Publisher (doi) , Last manuscript. This is a review paper. I survey many current frameworks including habits, long run risks, idiosyncratic risks, heterogenous preferences, rare disasters, probability mistakes, and debt or institutional finance. I stress how all these approaches produce quite similar results and mechanisms: the market's ability to bear risk varies over time, with business cycles. I speculate with some simple models that time-varying risk premiums can produce a theory of risk-averse recessions, produced by varying risk aversion and precautionary saving, rather than Keynesian flow constraints or new-Keynesian intertemporal substitution. The July 2016 manuscript contains a long section with thoughts on how to make a macro model based on time varying risk premiums, that got cut from the above final version. (This is the "manuscript" referenced in the paper.) The Data and programs (zip, matlab). The slides for the talk. A very nice post on the Review of Finance Blog summarizing the paper, by Alex Edmans, the editor. Typo: equation (17) is wrong. The same equation, (3) is right.
2017. Review of Finance 21(3): 945-985. Links: Publisher (doi) , Last manuscript. This is a review paper. I survey many current frameworks including habits, long run risks, idiosyncratic risks, heterogenous preferences, rare disasters, probability mistakes, and debt or institutional finance. I stress how all these approaches produce quite similar results and mechanisms: the market's ability to bear risk varies over time, with business cycles. I speculate with some simple models that time-varying risk premiums can produce a theory of risk-averse recessions, produced by varying risk aversion and precautionary saving, rather than Keynesian flow constraints or new-Keynesian intertemporal substitution. The July 2016 manuscript contains a long section with thoughts on how to make a macro model based on time varying risk premiums, that got cut from the above final version. (This is the "manuscript" referenced in the paper.) The Data and programs (zip, matlab). The slides for the talk. A very nice post on the Review of Finance Blog summarizing the paper, by Alex Edmans, the editor. Typo: equation (17) is wrong. The same equation, (3) is right.
A New Structure for U.S. Federal Debt
November 2015 In David Wessel, Ed., The $13 Trillion Question: Managing the U.S. Government's Debt, pp. 91-146. Washington DC: Brookings Institution Press. Last manuscript. I propose a restructuring of U. S. Federal debt. All debt should be perpetual, paying coupons forever with no principal payment. The debt should be composed of 1) Fixed-value, floating-rate, electronically transferable debt. Such debt looks like a money-market fund, or reserves at the Fed, to an investor. 2) Nominal perpetuities: This debt pays a coupon of $1 per bond, forever. 3) Indexed perpetuities: This debt pays a coupon of $1 times the current consumer price index (CPI). 4) All debt should be free of income, estate, capital gains, and other taxes. 5) long term debt should have explicitly variable coupons. 6) Swaps. The Treasury should adjust maturity structure, interest rate and inflation exposure of the Federal budget by transacting in simple swaps among these securities.
November 2015 In David Wessel, Ed., The $13 Trillion Question: Managing the U.S. Government's Debt, pp. 91-146. Washington DC: Brookings Institution Press. Last manuscript. I propose a restructuring of U. S. Federal debt. All debt should be perpetual, paying coupons forever with no principal payment. The debt should be composed of 1) Fixed-value, floating-rate, electronically transferable debt. Such debt looks like a money-market fund, or reserves at the Fed, to an investor. 2) Nominal perpetuities: This debt pays a coupon of $1 per bond, forever. 3) Indexed perpetuities: This debt pays a coupon of $1 times the current consumer price index (CPI). 4) All debt should be free of income, estate, capital gains, and other taxes. 5) long term debt should have explicitly variable coupons. 6) Swaps. The Treasury should adjust maturity structure, interest rate and inflation exposure of the Federal budget by transacting in simple swaps among these securities.
The Fragile Benefits of Endowment Destruction
November 2015. Journal of Political Economy 123(5) 1214-1226. With John Y. Campbell. (JSTOR / JPE Link.) A rejoinder to Ljungqvist and Uhlig "Comment on the Campbell-Cochrane Habit Model" (formerly titled "Optimal Endowment Destruction under Campbell-Cochrane Habit Formation"). The benefits of endowment destruction depend sensitively on how you discretize the model. Lesson: It's better to use the the continuous time version and make sure discretizations make sense. There is a nice lesson on how to extend diffusion models to jumps too. Computer program.
November 2015. Journal of Political Economy 123(5) 1214-1226. With John Y. Campbell. (JSTOR / JPE Link.) A rejoinder to Ljungqvist and Uhlig "Comment on the Campbell-Cochrane Habit Model" (formerly titled "Optimal Endowment Destruction under Campbell-Cochrane Habit Formation"). The benefits of endowment destruction depend sensitively on how you discretize the model. Lesson: It's better to use the the continuous time version and make sure discretizations make sense. There is a nice lesson on how to extend diffusion models to jumps too. Computer program.
Toward a run-free financial system
November 4 2014. In Martin Neil Baily, John B. Taylor, eds., Across the Great Divide: New Perspectives on the Financial Crisis, Hoover Press. This is an essay about what I think we should do in place of current financial regulation. We had a run, so get rid of run-prone liabilities. Technology and financial innovation means we can overcome the standard objections to "narrow banking." Some fun ideas include a tax on debt rather than capital ratios, the Fed and Treasury should issue reserves to everyone and take over short-term debt markets just as they took over the banknote market in the 19th century, and downstream fallible vechicles can tranche up bank equity.
November 4 2014. In Martin Neil Baily, John B. Taylor, eds., Across the Great Divide: New Perspectives on the Financial Crisis, Hoover Press. This is an essay about what I think we should do in place of current financial regulation. We had a run, so get rid of run-prone liabilities. Technology and financial innovation means we can overcome the standard objections to "narrow banking." Some fun ideas include a tax on debt rather than capital ratios, the Fed and Treasury should issue reserves to everyone and take over short-term debt markets just as they took over the banknote market in the 19th century, and downstream fallible vechicles can tranche up bank equity.
Challenges for Cost-Benefit Analysis of Financial Regulation.
Journal of Legal Studies 43 S63-S105 (November 2014). Is cost benefit analysis a good idea for financial regulation? I survey the nature of costs and benefits of financial regulation and conclude that the legal process of current health, safety and environmental regulation can't be simply extended to financial regulation. I opine about how a successful cost-benefit process might work. My costs and benefits expanded to a rather critical survey of current financial regulation. It's based on a presentation I gave at a conference on this topic at the University of Chicago law school Fall 2013, with many interesting papers. JSTOR link with HTML and nicer pdf. The JLS issue with all conference papers.
Journal of Legal Studies 43 S63-S105 (November 2014). Is cost benefit analysis a good idea for financial regulation? I survey the nature of costs and benefits of financial regulation and conclude that the legal process of current health, safety and environmental regulation can't be simply extended to financial regulation. I opine about how a successful cost-benefit process might work. My costs and benefits expanded to a rather critical survey of current financial regulation. It's based on a presentation I gave at a conference on this topic at the University of Chicago law school Fall 2013, with many interesting papers. JSTOR link with HTML and nicer pdf. The JLS issue with all conference papers.
A mean-variance benchmark for intertemporal portfolio theory
Journal of Finance, 69: 1–49. doi: 10.1111/jofi.12099 (February 2014) (link to JF) (Manuscript) Applies good old fashioned mean-variance portfolio analysis to the entire stream of dividends rather than to one-period returns. Long-Run Mean-Variance Analysis in a Diffusion Environment is a set of notes, detailing all the trouble you get in to if you try to apply long-run ideas to the standard iid lognormal environment, and also discusses shifting bliss points a bit.
Journal of Finance, 69: 1–49. doi: 10.1111/jofi.12099 (February 2014) (link to JF) (Manuscript) Applies good old fashioned mean-variance portfolio analysis to the entire stream of dividends rather than to one-period returns. Long-Run Mean-Variance Analysis in a Diffusion Environment is a set of notes, detailing all the trouble you get in to if you try to apply long-run ideas to the standard iid lognormal environment, and also discusses shifting bliss points a bit.
Finance: Function Matters, not Size
May 2013 Journal of Economic Perspectives 27, 29–50 JEP link (Previous title "Is Finance Too big?" December 2012.) Is finance "too big?" Is this the right question? .
May 2013 Journal of Economic Perspectives 27, 29–50 JEP link (Previous title "Is Finance Too big?" December 2012.) Is finance "too big?" Is this the right question? .
Discount Rates
Joural of Finance 66, 1047-1108 (August 2011). My American Finance Association Presidential speech. The video (including gracious roast by Raghu Rajan) The slides. Data and programs (zip file) Price should equal expected discounted payoffs. Efficiency is about the expected part. The unifying theme of today's finance research is the discounted part -- characterizing and understanding discount-rate variation. The paper surveys facts, theories, and applications, mostly pointing to challenges for future research.
Joural of Finance 66, 1047-1108 (August 2011). My American Finance Association Presidential speech. The video (including gracious roast by Raghu Rajan) The slides. Data and programs (zip file) Price should equal expected discounted payoffs. Efficiency is about the expected part. The unifying theme of today's finance research is the discounted part -- characterizing and understanding discount-rate variation. The paper surveys facts, theories, and applications, mostly pointing to challenges for future research.
Lessons from the financial crisis
Jan 2010 Regulation 32(4), 34-37. The financial crisis is mainly about too big to fail expectations. The only way out is to limit the government’s authority to bail out.
Jan 2010 Regulation 32(4), 34-37. The financial crisis is mainly about too big to fail expectations. The only way out is to limit the government’s authority to bail out.
State-Space vs. VAR models for Stock Returns
Manuscript July 24 2008. In a “state-space” model, you write a process for expected returns and another one for expected dividend growth, and then you find prices (dividend yields) and returns by present value relations. I connect state-space models with VAR models for expected returns. What are the VAR or return-forecast-regression implications of a state-space model? What state-space model does a VAR imply? I start optimistic. An AR(1) state-space model gives a nice return-forecasting formula, in which you use both the dividend yield and a moving average of past returns to forecast future returns. The general formulas leave me pessimistic however. One can write any VAR in state-space form, and we don’t really have solid economic reasons to restrict either VAR or state-space representations. Still, the connections between the two representations are worth exploring, and if you’re doing that this paper might save you weeks of algebra.
Manuscript July 24 2008. In a “state-space” model, you write a process for expected returns and another one for expected dividend growth, and then you find prices (dividend yields) and returns by present value relations. I connect state-space models with VAR models for expected returns. What are the VAR or return-forecast-regression implications of a state-space model? What state-space model does a VAR imply? I start optimistic. An AR(1) state-space model gives a nice return-forecasting formula, in which you use both the dividend yield and a moving average of past returns to forecast future returns. The general formulas leave me pessimistic however. One can write any VAR in state-space form, and we don’t really have solid economic reasons to restrict either VAR or state-space representations. Still, the connections between the two representations are worth exploring, and if you’re doing that this paper might save you weeks of algebra.
Two Trees
(with Francis Longstaff and Pedro Santa-Clara), Review of Financial Studies 21 (1) 2008 347-385. We solve the model with two Lucas trees, iid dividends and log utility. Surprise: it has interesting dynamics. If one stock goes up it is a larger share of the market. Its expected return must rise so that people are willing to hold it despite its now larger share. Typo: Equation 39 (page 363), the numerator should read (1-s/(1-s))ln(s)/V, not 1-s/(1-s)ln(s)/V. Thanks to Egor Malkov.
(with Francis Longstaff and Pedro Santa-Clara), Review of Financial Studies 21 (1) 2008 347-385. We solve the model with two Lucas trees, iid dividends and log utility. Surprise: it has interesting dynamics. If one stock goes up it is a larger share of the market. Its expected return must rise so that people are willing to hold it despite its now larger share. Typo: Equation 39 (page 363), the numerator should read (1-s/(1-s))ln(s)/V, not 1-s/(1-s)ln(s)/V. Thanks to Egor Malkov.
Decomposing the Yield Curve
Manuscript, first big revision, March 14 2008. With Monika Piazzesi. We work out an affine term structure model that incorporates our bond risk premia from “Bond Risk Premia” in the AER. There are lots of interesting dynamics – level, slope and curvature forecast future bond risk premia, and we discover that market prices of risk are really simple. We use the model to decompose the yield curve – given a yield (forward) curve today, how much is expected future interest rates, and how much is risk premium? How does the yield or forward rate premium correspond to the term structure of expected return premia? Was the conundrum a conundrum? Slides from 2010 AFA meetings Data and Programs.
Manuscript, first big revision, March 14 2008. With Monika Piazzesi. We work out an affine term structure model that incorporates our bond risk premia from “Bond Risk Premia” in the AER. There are lots of interesting dynamics – level, slope and curvature forecast future bond risk premia, and we discover that market prices of risk are really simple. We use the model to decompose the yield curve – given a yield (forward) curve today, how much is expected future interest rates, and how much is risk premium? How does the yield or forward rate premium correspond to the term structure of expected return premia? Was the conundrum a conundrum? Slides from 2010 AFA meetings Data and Programs.
Financial markets and the Real Economy
In Rajnish Mehra, Ed. Handbook of the Equity Premium Elsevier 2007, 237-325. Everything you wanted to know, but didn’t have time to read, about equity premium, consumption-based models, investment-based models, general equilibrium in asset pricing, labor income and idiosyncratic risk.
In Rajnish Mehra, Ed. Handbook of the Equity Premium Elsevier 2007, 237-325. Everything you wanted to know, but didn’t have time to read, about equity premium, consumption-based models, investment-based models, general equilibrium in asset pricing, labor income and idiosyncratic risk.
This article appeared four times, getting better each time. (Why waste a good article by only publishing it once?) The link above is the last and the best. The previous versions were NBER Working paper 11193, Financial Markets and the Real Economy Volume 18 of the International Library of Critical Writings in Financial Economics, John H. Cochrane Ed., London: Edward Elgar. March 2006, and in Foundations and Trends in Finance 1, 1-101, 2005.
Portfolio theory
Feb. 20 2007 This is a draft of a portfolio theory chapter for the next revision of Asset Pricing. I (of course) take a p = E(mx) approach to portfolio theory before covering the classic Merton-style direct approach. I emphasize the importance of outside income.
Feb. 20 2007 This is a draft of a portfolio theory chapter for the next revision of Asset Pricing. I (of course) take a p = E(mx) approach to portfolio theory before covering the classic Merton-style direct approach. I emphasize the importance of outside income.
The Dog that Did Not Bark: A Defense of Return Predictability
Review of Financial Studies 21(4) 2008 1533-1575. Taken alone, returns may not look that predictable. However, price-dividend ratios vary, so either returns or dividend growth must be forecastable (or both). Implications for dividends, and long-run forecasts give strong statistical evidence against the null that returns are not forecatsable. I address the Goyal-Welch finding that forecasts do badly out of sample, and the long literature criticizing long-run forecasts. The most important practical takeaway: even if you assume that all variation in market p/d ratios comes from time-varying expected returns, and none corresponds to dividend growth forecasts, you will typically find that market-timing strategies based on fitting the regression don’t work. Corrected Table 6. Three numbers were wrong in the published version. Thanks to Camilla Pederson for catching it.
Review of Financial Studies 21(4) 2008 1533-1575. Taken alone, returns may not look that predictable. However, price-dividend ratios vary, so either returns or dividend growth must be forecastable (or both). Implications for dividends, and long-run forecasts give strong statistical evidence against the null that returns are not forecatsable. I address the Goyal-Welch finding that forecasts do badly out of sample, and the long literature criticizing long-run forecasts. The most important practical takeaway: even if you assume that all variation in market p/d ratios comes from time-varying expected returns, and none corresponds to dividend growth forecasts, you will typically find that market-timing strategies based on fitting the regression don’t work. Corrected Table 6. Three numbers were wrong in the published version. Thanks to Camilla Pederson for catching it.
International Risk Sharing is Better Than You Think, Or Exchange Rates are Too Smooth
With Michael Brandt and Pedro Santa Clara. Published Journal of Monetary Economics 53 (4) May 2006 671-698. Original July 2001 (NBER WP 8404) The equity premium means that marginal rates of substitution are very volatile, with more than 50% standard deviation. Exchange rates are the ratio of marginal rates of substitution, and they only vary by about 12%. Therefore, marginal rates of substitution must be highly correlated across countries. Risk sharing is better than you think.
With Michael Brandt and Pedro Santa Clara. Published Journal of Monetary Economics 53 (4) May 2006 671-698. Original July 2001 (NBER WP 8404) The equity premium means that marginal rates of substitution are very volatile, with more than 50% standard deviation. Exchange rates are the ratio of marginal rates of substitution, and they only vary by about 12%. Therefore, marginal rates of substitution must be highly correlated across countries. Risk sharing is better than you think.