Siegel thinks S&P earnings should be weighted by company's market cap. The immediate question is which market cap should be used: the market cap at the beginning of the quarter, or at the end of the quarter? This will make big difference in current volatile market, where, for example, some big banks' market cap can be halved in a couple of weeks, if not days. (source: WSJ)
The S&P Gets Its Earnings Wrong
Stocks are cheaper than they look.
By JEREMY J. SIEGEL
Standard & Poor's recently shocked investors with an announcement that reported earnings for its S&P 500 Index for the fourth quarter of 2008 are forecast to be negative for the first time since such data were calculated in 1936. S&P further reports that for all of 2008, earnings are expected to be less than $40 per share, indicating that the market now has a price/earnings ratio over 20, well above its historical average of 15.
What this dismal news actually reflects is the bizarre way in which S&P (and most other index providers) calculate "aggregate" earnings and P/E ratios for their indexes. Unlike their calculation of returns, S&P adds together, dollar for dollar, the large losses of a few firms to the profits of healthy firms without any regard to the market weight of the firm in the S&P 500. If they instead weight each firm's earnings by its relative market weight, identical to how they calculate returns on the S&P 500, the earnings picture becomes far brighter.
A simple example can illustrate S&P's error. Suppose on a given day the only price changes in the S&P 500 are that the largest stock, Exxon-Mobil, rose 10% in price and the smallest stock, Jones Apparel Group, fell 10%. Would S&P report that the S&P 500 was unchanged that day? Of course not. Exxon-Mobil has a market weight of over 5% in the S&P 500, while the weight of Jones Apparel is less than .04%, so that the return on Exxon-Mobil is weighted 1,381 times the return on Jones Apparel. In fact, a 10% rise in Exxon-Mobil's price would boost the S&P 500 by 4.64 index points, while the same fall in Jones Apparel would have no impact since the change is far less than the one-hundredth of one point to which the index is routinely rounded.
Yet when S&P calculates earnings, these market weights are ignored. If, for example, Exxon-Mobil earned $10 billion while Jones Apparel lost $10 billion, S&P would simply add these earnings together to compute the aggregate earnings of its index, ignoring the vast discrepancy in the relative weights on these firms. Although the average investor holds 1,381 times as much stock in Exxon-Mobil as in Jones Apparel, S&P would say that that portfolio has no earnings and hence an "infinite" P/E ratio. These incorrect calculations are producing an extraordinarily low reported level of earnings, high P/E ratios, and the reported fourth-quarter "loss."
As the fourth-quarter earnings season draws to a close, there are an estimated 80 companies in the S&P 500 with 2008 losses totaling about $240 billion. Under S&P's methodology, these firms are subtracting more than $27 per share from index earnings although they represent only 6.4% of weight in the index. S&P's unweighted methodology produces a dismal estimate of $39.73 for aggregate earnings last year.
If one applies market weights to each firm's earnings using the same procedure that S&P employs to compute returns, the results yield a more accurate view of the current profit picture. Market weights produce a reported earnings estimate of $71.10 for 2008 — nearly 80% higher than the unweighted procedure. The reason for this stark difference is that the firms with huge losses generally have extremely low market values and hence have a much smaller impact on the total earnings in the index.
Similarly, operating earnings (essentially, earnings before write-offs), of the S&P 500 are boosted to $81.94 per share when earnings are weighted by market value, yielding a P/E ratio of about 9.4 for the market, instead of S&P's $61.80, which yields a P/E ratio of 12.5 when firm profits are simply added. Even the negative earnings for the fourth quarter disappear when market weights are accounted for, as fourth-quarter GAAP earnings on the S&P 500 Index total $7.44 per share and operating earnings reach $14.40.
No one can deny that the recent economic downturn has badly hurt corporate earnings. But let's not fool ourselves into thinking that this is an expensive market. When computed accurately, P/E ratios show that this market is much cheaper than is currently being reported by the S&P. Those who venture into today's stock market are indeed buying good values.
Mr. Siegel is professor of finance at the University of Pennsylvania's Wharton School.