Finance Memos

How to correctly calculate portfolio PE ratios?

Question:   Two analysts are given the task of calculating the PE ratio of the DOW using the data below.   (Note:  Data on one firm is missing because of a recent merger.)

The first analyst uses method one and takes the ratio of the weighted average of market caps for the 29 companies to the ratio of earnings for the 29 companies.

The second analyst uses method two and takes the weighted average of the PE ratios of the 29 stocks.

What is the correct way to calculate the PE ratio for this portfolio?

What are the ramifications of using the wrong method to calculate the PE ratio for this portfolio?

The Data:

Methodological Note:  Assume the columns of your spreadsheet are – (1) Share of DOW in A, (2) Market Cap in B, Trailing Earnings in C, and Trailing PE in D.

Also assume there are 29 rows, 1 to 29 for each variable.

The formula for method one is =SUMPRODUCT(a1:a29,b1:b29)/SUMPRODUCT(a1:a29,c1:c29)

The formula for method two is

=SUMPRODUCT(a1:a29,d1:d29)

Analysis:   The DOW PE ratio for method one is 20.5, a pretty high number compared to the historic norm of PE ratios for this index.

The DOW PE ratio for method two is 46.7, a number that is implausible for the portfolio of DOW stocks

The PE ratio of one company in the DOW, CAT is 696, an extreme outlier.  This outlier drives up the weighted average of the PE ratios by a lot.

It is inappropriate to take the average of PE ratios because often a PE ratio for a particular company is an outlier or is below zero.

PE ratios below zero are economically meaningless.    For a discussion of how to calculate the PE ratio of a portfolio when some stocks in the portfolio have negative earnings go to the following site.

PE Ratios When Some Firms Have Negative Earnings

http://www.dailymathproblem.com/2017/05/price-earning-ratios-for-portfolios.html

Many analysts deal with the issues of negative or outlier PE ratios by dropping firms from their analysis.     There is no need to drop firms when you calculate a portfolio PE ratio if you are using an appropriate method.

Evaluating Fund Performance

Investment funds, both ETFs and mutual funds, are usually compared on the basis of returns of arbitrarily selected holding periods.   Typically, the fund manager reports year-to-date returns and return for one, three, five, and ten years.  The discussion of fund risk is usually based on a subjective assessment of the risk of the assets in the fund.

The conventional approach to presenting statistics on fund performance is inadequate.   Funds can be purchased at any time, not just a few arbitrarily selected dates.   This post measures the mean and standard deviation of return for two popular funds when there are multiple possible purchase and sale dates for each fund.

Statistical tests are used to evaluate whether the observed difference in return and risk outcomes for two funds are statistically significant.

Question:   This post considers two of Vanguards most successful funds.  VFIAX is a fund that mimics the S&P 500 and VWELX a fund that is around 70% equity and 30% fixed income.

The 48 potential purchase dates for both of the two funds are the first day of each month starting in January 2002 and ending in December of 2005.

The 48 potential sale dates for the two funds are the first day of each month starting in January 2012 and ending in December of 2015.

• Assume that each combination of purchase and sale dates is equally likely.

• What are the expected return and the standard deviation of return for both funds?

• What are the minimum and maximum returns for each fund?

• Can we reject the hypothesis of identical variances for the two funds?

• Can we reject the hypothesis the mean returns are identical?

Analysis:

There are 2304 (48 x 48) possible (purchase-sale) outcomes.  For each of these outcomes I calculate ln(AP₂/AP₁) where AP₂ is the adjusted price in the 2012 to 2015 time period and AP₁ is adjusted price in the 2002 to 2005 time period.

The mean standard deviation, minimum, and maximum for the two funds are presented below.

Sample size 2304 based on 48 possible purchase dates between 2002 and 2005 and 48 possible sale dates 2012 and 2015.

Observations:

• The mean return of the bond/stock fund is higher than the mean return of the stock-only fund by around 10 percent.

• The standard deviation of returns for the bond/stock fund is lower than the standard deviation of returns for the stock-only fund by around 21 percent.

• The maximum return is higher for the stock-only fund by around 92 percent.

• The minimum return is lower for the stock-only fund by around 6 percent.

Comments:

Comment One:  The finding that the combined stock/bond fund has a larger mean return compared to the stock-only fund is extremely unusual because over long periods stocks tend to have higher returns than bonds.    However, the stock portfolios of the two funds differ.  The stock portfolio in VWELX is broadly diversified but does not track a specific index.   The stock portfolio in VFIAX tracks the S&P 500.  VWELX was able to get higher returns than VFIAX because its stock portfolio outperformed the S&P 500 while the bond portfolio lowered risk.   It also did not hurt that interest rates fell and bond prices rose in this time period.

Comment Two:  The stock-only portfolio was much more risky than the combined bond-stock portfolio.   This is evidenced both by the lower standard deviation and the higher minimum return.  The minimum return statistic measures the worst-outcome return.  The worst-outcome return for the combined stock-bond portfolio is around 92 percent higher than the worst-outcome return for the stock-only portfolio.

Tests of equal variances for returns:

A test of the hypothesis that the variances of return for the two portfolios are equal was conducted.   The F-statistic comparing the ratio of the two standard deviations was 1.63, which is significantly different from 1.0.    The hypothesis that the two variances are identical is rejected.

Tests of equal mean returns:

A test of the hypothesis that the mean returns for the two portfolios are equal was conducted.  The t-statistic for this hypothesis test was 12.9.   The hypothesis of identical means is rejected.

Technical Note:  I used STATA to make the calculations in this note.  Period one and period two data were placed in separate data sets.   The N to N merge provides the 2304 outcomes.

Concluding Thought:  The practice of presenting return numbers on investment funds for a few arbitrarily chosen holding periods is, in my view, not very useful.    The holding periods are arbitrary and subject to manipulation.   There is no measure of risk.

The technique presented here relies on many possible outcomes defined by different purchase and sale dates.   The multiple outcome approach allows for the presentation of risk measures.

The note shows that the performance of the VWELX fund was exceptional in this period.

Question:  The table below has price data and daily return data for Vanguard fund VB.   Calculate the arithmetic and geometric averages of the daily return data.   Show that the geometric average accurately reflects the relationship between the initial and final stock price and the arithmetic average does not accurately explain this relationship.

Analysis:   The table below presents calculation of the two averages and the count of return days.  The product of the initial value of the ETF, the pertinent average and the count of return days is the estimate of the final value.   Estimates of final ETF value are calculated for both the arithmetic average and the geometric average and these estimates are compared to the actual value of the stock on the final day in the period.

There is another way to show that the daily return should be modeled with the geometric mean rather than arithmetic mean.  The average daily return of the stock is (FV/IV)^(1/n) – 1 where FV is final value and IV is initial value and n is the number of market days in the period, which for this problem is 21.

Using this formula we find the daily average holding period return is 0.001479966.  Note that 1 minus the geometric mean of the daily stock price ratio is also 0.001479966.

The geometric mean gives us the correct holding period return.

Profit and risk when there are four random purchase dates and four random sale dates

Question:   In 2013 a person buys QQQ the high tech ETF) on one of four randomly selected dates determined by when the broker arranges a meeting.   I

The person who bought the QQQ shares in 2014 got fired in 2015.   As soon as the person was fired he realized he needed cash so he called his broker and said “SELL QQQ” The firing is a random event independent of the market and out of control of the person, which occurred on one of four dates.

The four potential purchase and four potential sales dates for the QQQ transactions are presented below.

The person spends $25,000 on the purchase of QQQ in 2014 and sells all shares in 2015.

Assume no dividends are paid.

What are all possible profit outcomes from the purchase and sale of the QQQ securities?

What is the expected profit?

What is the variance of profit?

Analysis:  The number of share purchased is $25,000 divided by the purchase price; hence the purchase price determines the number of shares purchased.

Revenue received after the sale is price at time of sale times the number of shares owned.

Profit after the sale is revenue minus the $25,000 initial investment.

There are four possible purchase dates and four possible sale dates.   The purchase and sale dates are independent so there are a total of 16 possible equally likely combinations of sale and purchase dates.   The probability of each purchase/sale combination is 0.0625 (0.25*0.25).

The profit calculation for the 16 purchase-sale combinations is presented in the table below.

The minimum profit is -$400.   The maximum profit is $7,985.

The expected profit is obtained by taking the dot product or the sumproduct of the probability vector with the profit vector.   The variance was obtained from the computational formula.

Var (Profit) = E(profit²) – E(Profit)²

For a discussion of these calculations see the previous post.

http://dailymathproblem.blogspot.com/2015/11/expected-value-and-variance-of-share.html

The expected value and variance or profit from the purchase of QQQ on one of four dates in 2014 and the sale of QQQ on one of four dates in 2015 are presented below.

Financial Discussion:

The purchaser of QQQ or any stock that buys randomly and is forced to sell because of random events unrelated to the market bears substantial risk compared to an investor with enough liquid assets who will not need to sell in an emergency.   Investors would be wise to consider the level of the market and their ability to hold through downturns prior to selling.  The experts say that stock market returns beat returns on other securities over the long haul.  But this investor was only able to hold for a year.

Outcomes could have been worse.   The broker put the investor in QQQ a relatively diversified ETF that focuses on tech stocks.  Had the broker put his client in one particular stock (say IBM) and the investor was forced to sell he would have realized a large loss.

Measuring Returns for Different Investment-Consumption Patterns

Question:   An investment advisor tells his client to invest $1,000 per month in VFIAX (Vanguard S&P fund) for five years.   The person will then live off the proceeds in this fund for 36 consecutive months.

Calculate the return on assets from this investment/consumption plan for two different start dates – January 1, 2002 and January 1, 2003.

What is the NPV of investment returns from this investment strategy/ consumption plan on the same start dates?

What should investors who are planning to save for five years and spend for three years learn from this example?

Mutual funds and ETFs tend to advertise holding period returns based on specific purchase dates and specific sale dates.   These returns are based on the price of securities on two dates only.   What does the example presented here tell you about the usefulness of two-period return statistics reported by mutual funds?

Methodological Note:  The shares purchased each month are $1,000/PVFIAX where PVFIAX is the price of the ETF.   I sum over 60 months to get the total shares purchased, which I will denote TSHARES. The formula for cash inflow for the 36 months are (1/36)*TSHARE*PVFIAX.

The cash inflow/outflow column and the date column are inputted into the XIRR function in Excel to give the IRR of the inflows/outflows on these particular dates. The XNPV function gives net present value of the cash flows.

Analysis:

The value of VFIAX reached its pre financial crisis high in 10/2007 and reached its crisis trough in 02/2009.   Hindsight is 20/20 but it appears as though diversification prior to the downturn would have been beneficial.

What follows are return calculations for the two scenarios.

Results are in the table below.

Observations:

• The person who stopped saving in December 2006 did fairly well despite the financial crisis.The IRR for this investor was 12.04 %.   The NPV of the investments was $15,766.   (NPV calculation assumes a5 percent cost of capital.) 

• The person who stopped investing in December 2007 realized a return only slightly higher than 0 percent.The NPV of this person’s investment was around $800.

Discussion of Investment Strategy:

In my view, a 100 percent VFIAX strategy is unwise for an investor with this type of investment and consumption period.

How to fix this problem is a more difficult question.  It is important to note that the strategy of putting 100 percent of funds in VFIA for an investor with a start date of January 1 2009 or January 1, 2010 did quite well.

529 plans offer life-cycle funds that drift towards a more conservative investment as the person nears the date where he must spend money.   Lifecycle funds would have done reasonably well for both of the scenarios considered here.  However, the life-cycle approach creates miserable results when the market does poorly in the first few years of the investment period and then rebounds.

My view on how to solve this problem is evolving.  A 60/40 (stock/bond) portfolio would have done well in these time periods but I don’t believe that it will work in the next crash.  Interest rates are now very low and I expect in the next crisis bonds and stocks will crash together.   Perhaps allocating some resources into an inflation-indexed bond fund would help balance returns during the next crisis.

The trend in investment is toward investment in passively managed funds like the ones offered by Vanguard.    This is at best a partial solution.   Investors need help in allocating money across several passively managed funds.  This includes advice on initial allocations and reallocation over time.

I believe there is a need for an actively managed fund that invests exclusively in passively managed funds and reallocated assets across funds as market conditions change.

Note on traditional holding period statistics:  The value of VFIAX in January 2002 was 17.9.  In December of 2010 the value of VFIAX was 39.5.   The return for this 7.9 year  holding period was at 10.5%.

However a person who started investing in January 2003 and started spending in January 2008 earned squat!   

The mutual funds can legally and honestly report great eight-year or ten-year holding return but their clients aren’t doing particularly well.

Such a surprise!