Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Modern Portfolio Theory and Practice

7,163 views

Published on

My experience applying the ideas of modern portfolio theory.

Published in: Economy & Finance, Business
  • Login to see the comments

Modern Portfolio Theory and Practice

  1. 1. Modern Portfolio Theory and Practice -or- Get Rich Slow -or- Why the Real Mutual Fund Scandal is Legal David Roodman Summer 2007
  2. 2. Lesson 1: Do save/invest <ul><li>Have 3-6 months of expenses in cash </li></ul><ul><ul><li>Split between money market and short-term bond fund </li></ul></ul><ul><li>Save in tax-favored vehicles early and often </li></ul><ul><ul><li>For savings made early in life, the subsidy is large </li></ul></ul><ul><ul><li>A window of opportunity closes every 12/31. </li></ul></ul><ul><li>If you lack 401(k)/403(b) access, favor Roths. </li></ul>
  3. 4. Modern Portfolio Theory (Harry Markowitz, 1952) <ul><li>Universe of investible securities characterized by 3 sets of numbers: </li></ul><ul><ul><li>Expected return of each security (say, per month) </li></ul></ul><ul><ul><li>Standard deviation of future (monthly) returns </li></ul></ul><ul><ul><li>A correlation matrix for expected returns. </li></ul></ul><ul><li>Investor’s task: choose portfolio that maximizes expected total return for a given level of “risk” (standard deviation of overall portfolio return) </li></ul>
  4. 5. MPT, cont’d <ul><li>Diversification principle: </li></ul><ul><ul><li>Suppose Netzoot and Zipcom are tech stocks that have an expected return of 10%/year and an s.d. of return of 4%, and have an expected correlation of 0.5. Then a 50/50 portfolio of the two will have: </li></ul></ul><ul><ul><ul><li>expected return = 10% </li></ul></ul></ul><ul><ul><ul><li>s.d. of return =3.47% (    of portfolio=3/4 of   of either) </li></ul></ul></ul><ul><ul><ul><li>Same return, lower risk! </li></ul></ul></ul><ul><ul><li>90/10 bond/stock portfolio less risky than 100% bond </li></ul></ul><ul><li>Lesson 2: Diversify . Own some of everything. </li></ul>
  5. 6. Can diversification eliminate risk? <ul><li>No. There is an irreducible component of variation in returns that is shared by all stocks. No amount of diversification will eliminate it because all stocks have it: market risk. Stocks tend to rise and fall together. </li></ul><ul><li>Model: r IBM =  +  r market    constants </li></ul><ul><li>In theory,  embodies the only component of risk investors care about: systemic or market risk. Variation not explained by this model, idiosyncratic risk, does not matter because it washes out in a diversified portfolio. </li></ul>
  6. 7. MPT, cont’d <ul><li>Markowitz developed algorithm to pick optimal portfolio for given level of risk </li></ul><ul><li>We don’t know expected return, s.d. of return, future correlations. </li></ul><ul><li>Can try using past values as estimators. </li></ul><ul><li>Applied his algorithm to this information. </li></ul><ul><li>Didn’t work so well: weird portfolios or unremarkable returns. </li></ul>
  7. 8. Efficient market hypothesis (Eugene Fama, 1965, Chicago dissertation) <ul><li>Market is a “random walk”: “efficient” </li></ul><ul><li>“ Efficient” does not mean prices are correct. </li></ul><ul><li>Rather: all available information is already incorporated into stock prices </li></ul><ul><li>Changes in prices caused only by unpredictable arrivals of new information, or pure noise in trading </li></ul><ul><li>Beating the market is impossible except by chance </li></ul><ul><li>“ Research” by stock & bond analysts is a waste of time </li></ul><ul><li>Monkeys throwing darts at stock page do as well on average </li></ul>
  8. 9. EMH, cont’d <ul><li>Backed by lots of empirical evidence that investors/mutual funds rarely beat the market consistently—no more than should happen by chance </li></ul><ul><li>Think of it this way: ~90% of trading by large institutions with same information and methods. Can’t all be above average. </li></ul><ul><li>Lesson 3: Practice humility </li></ul>
  9. 10. Daily % change in AT&T stock vs. previous % change, ~1998-2003
  10. 11. 3 forms of EMH <ul><li>Weak: all past market prices and data are reflected in securities prices today. Technical analysis useless. </li></ul><ul><li>Semistrong: all publicly available information is reflected. Fundamental analysis useless. </li></ul><ul><li>Strong: all information is reflected. Even insider information useless. </li></ul><ul><li>I believe it is prudent in general to invest as if all are true (unless you have inside information!) </li></ul>http://www.investorhome.com/emh.htm
  11. 12. Implications <ul><li>The investment advice industry is a huge waste. To a first approximation, it adds no value. Indeed, it reduces value by sucking out $ billions. </li></ul><ul><li>High-priced stock-pickers who work for “actively managed” mutual funds are mostly rip-offs for investors </li></ul><ul><li>Expense rate on good index fund: ~0.25% </li></ul><ul><li>On typical “active” fund: 0.75-2.0% </li></ul>
  12. 14. Why should they tell you? <ul><li>Fund companies with actively managed funds benefit from myth </li></ul><ul><li>Brokers get trading commissions </li></ul><ul><li>Money magazines carry fund ads </li></ul><ul><li>TV channels and web sites must pretend to relevance </li></ul><ul><li>Market imperfection: people don’t notice 1-2%/year expense when earnings are volatile or high, and documentation is in fine print </li></ul>
  13. 15. Lesson 4: minimize turnover <ul><li>When you or your fund manager buy and sell it: </li></ul><ul><li>Creates taxable capital gains (if in taxable account) </li></ul><ul><li>Incurs trading commissions </li></ul><ul><li>Incurs losses because of bid-ask spread (not counted in expense ratios) </li></ul>
  14. 16. DALBAR survey of investors, 1984-2002 <ul><li>Average investor’s return on stocks: 2.57%/year. Turns $1000 into $1620 </li></ul><ul><li>S&P 500: 12.22%/year: $8940 </li></ul><ul><li>Inflation: 3.14%/year </li></ul><ul><li>I.e., average investor turned $1000 into $900 after inflation </li></ul><ul><li>S&P 500 turned $1000 into $5000 after infl. </li></ul><ul><li>Partly expenses; partly performance chasing </li></ul><ul><li>Big scandal in a country with a looming retirement crisis! </li></ul>http://www.dalbarinc.com/content/printerfriendly.asp?page=2003071601
  15. 17. <ul><li>Expenses: </li></ul><ul><li>Vanguard S&P 500 index fund: 0.18%/year </li></ul><ul><li>Calvert “socially responsible” U.S. equity fund (class C shares): 2.10%/year </li></ul><ul><li>Is this socially responsible? </li></ul>An indignant question
  16. 18. Capital Asset Pricing Model (Sharpe and others, ~1964) <ul><li>If every investor has all of Markowitz’s information about future returns and applies his algorithm, then in the equilibrium, all investors will split their $ between risk-free asset and the same portfolio of all other assets. </li></ul><ul><li>i.e., outside of cash holdings, everyone will have 1% IBM, 2% AT&T, etc. </li></ul><ul><li>Ergo, the market will be 1% IBM, 2% AT&T,…. </li></ul><ul><li>Ergo, everyone will own an index of the market. </li></ul>
  17. 19. Index mutual funds <ul><li>Sharpe’s model unrealistic, but helped create idea of index mutual funds </li></ul><ul><li>Commonsense ideas of diversification, humility, low turnover, and low cost argue for index funds </li></ul><ul><li>First ones started ~1973. Vanguard and State Street(?). </li></ul><ul><li>They don’t call me the Index guy for nothing. </li></ul><ul><li>Or: more generally, passive asset class investing </li></ul>
  18. 20. Interim conclusions <ul><li>Theoretical index fund covers all assets: foreign, domestic, stock, bond, housing </li></ul><ul><li>Real ones only cover subclasses </li></ul><ul><li>Lesson 5: Put your $ in a few very low-cost mutual funds, preferably index funds, covering all asset classes </li></ul><ul><li>Exact allocation that is best is a bit unclear because we do not believe Sharpe </li></ul><ul><li>Lesson 6: Obsess over expenses </li></ul><ul><li>Buy and hold. Minimize trading </li></ul><ul><li>Lesson 7: Exercise discipline. Never panic. </li></ul><ul><li>You will nearly match the market and beat most investors </li></ul>
  19. 21. Two things to ponder: 1. Risk vs. return <ul><li>Truism that the two go together </li></ul><ul><li>What is the evidence? </li></ul><ul><li>A generalization, not an iron law </li></ul><ul><li>There may be exceptions </li></ul><ul><li>No plausible theory says market will always accurately price risk since it is substantially unknowable and market itself creates price risk </li></ul>
  20. 22.   Geometric  From Malkiel, Random Walk Down Wall Street
  21. 23. Two things to ponder: 2. Herd behavior <ul><li>Bubbles and panics older than securities markets </li></ul><ul><ul><li>Dutch tulipmania in early 1600s </li></ul></ul><ul><li>Occur when people buy because the price has gone up, on the dangerous notion that past return predicts future return. </li></ul><ul><li>Buying causes appreciation, and vice versa… </li></ul><ul><li>Milder form: all actors unwittingly follow same strategy and reassured by results in short run—hedge funds today? </li></ul><ul><li>Don’t manias violate EMH? </li></ul>
  22. 24. Definitions <ul><li>Growth stocks: high-priced compared to current book value or earnings </li></ul><ul><li>Value stocks: opposite </li></ul><ul><li>Large-cap stocks: shares in big companies </li></ul><ul><li>Small-cap stocks: shares in small companies </li></ul><ul><li>Growth stocks called that because market evidently expects strong earnings growth </li></ul><ul><li>Value is a marketing euphemism? </li></ul>
  23. 25. Fama & French 1992 <ul><li>For each year in 1962-89, built simulated portfolios of U.S. stocks: growth, value, large, small, sorted by decile </li></ul><ul><li>3 deciles on value end beat 3 growth deciles 5%/yr </li></ul><ul><li>Good companies make bad investments and v.v. </li></ul><ul><li>Small beat large (not news) </li></ul><ul><li>Overall market return each year and small-large and value-growth return differences are factors </li></ul><ul><li>The 3 factors explain ~95% of the cross-sectional variation in mutual fund returns </li></ul>
  24. 26. From Robert Haugen, The New Finance: The Case against Efficient Markets, based on Fama & French 1992
  25. 27. Here’s where it gets weird <ul><li>Other research finds same value-growth pattern before 1960, and abroad. </li></ul><ul><li>Warren Buffet, Peter Lynch are value investors </li></ul><ul><li>But value stocks have had a lower standard deviation of returns than growth stocks: lower risk, higher returns! </li></ul><ul><li>According to EMH, Fama & French 1992 (new info.) should have sent $ pouring into value stocks, resulting in huge one-time gain, but lower returns to value stocks thereafter. Free lunches should not persist. </li></ul><ul><li>I read this in 1999, during “new economy” growth stock craze: exact opposite was happening. </li></ul><ul><li>(Maybe has happened now??) </li></ul>
  26. 28. From Robert Haugen, The New Finance: The Case against Efficient Markets, based on Fama & French 1992 Beta
  27. 29. 100 Most-Cited Researchers in Economics SOURCE: ISI Essential Science Indicators         Web based product from the September 1, 2002 update covering a ten year plus six month period, January 1992 - June 30, 2002.      RANK SCIENTIST PAPERS CITATIONS CITATIONS PER PAPER 1 SHLEIFER, A 50 1,717 34.34 2 FAMA , EF 20 1,242 62.10 3 LEVINE, R 22 1,205 54.77 4 KAHNEMAN, D 16 1,122 70.12 5 VISHNY, RW 23 1,043 45.35 6 MURPHY, KM 20 984 49.20 7 TVERSKY, A 13 901 69.31 8 SALAIMARTIN, X(*) 19 894 47.05 9 FRENCH , KR 14 881 62.93 10 ANDREWS, DWK 27 856 31.70
  28. 30. What’s going on? <ul><li>Fama says: some unobserved risk factor looms over these “distressed” value companies. Their true but unmeasured high risk is compensated by high returns. </li></ul><ul><li>I don’t buy it. They actually were riskier for 30 years but racked up much higher returns and lower volatility? </li></ul><ul><li>Fama is stuck. Maybe no Nobel </li></ul><ul><li>More plausible explanations come out of new field of behavioral finance, which he attacks rather vituperatively </li></ul><ul><li>“ Value premium” may be a permanent artifact of investor irrationality, i.e., human nature </li></ul>
  29. 31. My conclusion <ul><li>EMH is probably mostly true </li></ul><ul><li>Lesson 8: But the evidence on value stock outperformance (and maybe small stock outperformance) seems strong enough that I favor “tilting” </li></ul><ul><ul><li>E.g., instead of 50/50 value-growth, do 75/25. </li></ul></ul><ul><li>No one is saying value does systematically worse, so risk of long-term under-performance seems low </li></ul>
  30. 32. Lesson 9 :Vanguard is the best <ul><li>Essentially a cooperative </li></ul><ul><li>No incentive to take $ from customers and give it to own shareholders </li></ul><ul><li>Extremely low expenses </li></ul><ul><li>Wide selection of index and other funds </li></ul><ul><li>500 index fund now the world’s largest mutual fund. </li></ul><ul><li>From 0 in early 1970s, Vanguard has become largest mutual fund company in the world. </li></ul><ul><li>Also good: </li></ul><ul><ul><li>DFA (founded by Fama and others)—but for-profit and for millionaires </li></ul></ul><ul><ul><li>TIAA-CREF—non-profit, low-expenses, but few options WITH TIAA-CREF CANNOT DO WHAT I DID </li></ul></ul>
  31. 33. What I did <ul><li>Chose % allocations to different asset classes, covering as many as possible. </li></ul><ul><li>Put more abroad (33%) than is standard </li></ul><ul><li>“ Tilted” toward small and value (and small value) </li></ul><ul><li>70% stock, 30% bond (conventional for my age) </li></ul><ul><li>Just funds, no individual stocks </li></ul><ul><li>Rebalance once/year </li></ul><ul><li>Manage my IRA and wife’s, Vanguard, TIAA-CREF, etc., as a unit </li></ul>
  32. 34. Allocations
  33. 35. Data collection <ul><li>Database with daily price data and full transaction history. All distributions and fees counted </li></ul><ul><li>Maintain benchmark based on some Vanguard single-fund solutions that implement standard investment book pie charts via index funds (LifeStrategy, Target funds) </li></ul>
  34. 36. Real returns, 8/19/99–10/24/07
  35. 42. Bottom line <ul><li>My returns should continue to be less volatile. </li></ul><ul><li>Mostly likely: continuing gains relative to benchmark or parity </li></ul><ul><li>My wife and I can afford to die a half a year later </li></ul>
  36. 43. Total return on some funds in the portfolio Note: Not all funds held all 8 years.
  37. 44. “ Having spent nearly a decade writing about investment management for the little guy, I have come to the conclusion that I no longer believe in the basic premise of my public persona—a surreal cross between Harry Markowitz and Johnny Appleseed, as a friend put it. “ A decade ago, I really did believe that the average investor could do it himself. After all, the flesh was willing, the vehicles were available, and the math wasn’t that hard. “ I was wrong. Having emailed and spoken to thousands of investors over the years, I’ve come to the sad conclusion that only a tiny minority, at most one percent, are capable of pulling it off.” -- William J. Bernstein, Efficient Frontier, Winter 2003 http://www.efficientfrontier.com/ef/103/probable.htm
  38. 45. For more <ul><li>www.indexfunds.com and www.ifa.com </li></ul><ul><li>www.efficientfrontier.com </li></ul><ul><li>Haugen, The New Finance </li></ul><ul><li>Malkiel, Random Walk Down Wall Street </li></ul><ul><li>Bogle, Common Sense on Mutual Funds </li></ul><ul><li>Ellis, Winning the Loser’s Game </li></ul><ul><li>Bernstein, The Intelligent Asset Allocator </li></ul>

×