The Bearish View
About the only certainty in the stock market is that, over the long haul, overperformance turns into underperformance and vice versa. Is there a pattern to this movement? Let's apply some simple regression analysis to the question.
Here's a chart of the S&P Composite stretching back to 1871. The chart shows real (inflation-adjusted) monthly averages incorporating data collected by Yale economist Robert Shiller. We're using a semi-log scale to equalize the vertical distances for the same percentage changes regardless of the index price range. The regression trendline drawn through the data clarifies the secular pattern of variance from the trend — those multi-year periods when the market trades above and below trend.
The peak in 2000 marked an unprecedented 160% overshooting of the trend, which is double the overshoot in 1929. The index has been above the trend for 17 years. We also see that the major troughs saw declines in excess of 50% below the trend. If the S&P 500 were sitting squarely on the regression, it would be hovering around 820. If the index should decline over the next 12 months to a level comparable to previous major bottoms, it would fall to the vicinity of 400-425.
The Bullish Alternative
A critical factor for the reliability of a regression analysis of stock prices over many decades is the accuracy of the inflation adjustment. The Bureau of Labor Statistics (BLS) has been actively tracking inflation since 1919 and has estimated inflation rates back to 1913 using data on food prices. In 1982, however, the BLS began incorporating changes to the Consumer Price Index (CPI), which is used to calculate inflation. These changes have resulted in much lower "official" inflation rates than would have been the case if the method of calculation had remained consistent.
At his www.shadowstats.com website, Economist John Williams publishes Alternate CPI statistics employing the earlier BLS method. Here is a chart that illustrates the significant difference between these two calculation methods.
Now, let's take another look at the S&P Composite, this time adjusted for inflation since 1982 using Williams' Shadow Government Statistics. The change is astonishing. The adjustments to post-1982 data alter the slope of the regression that impacts the variance from the trend across the entire time frame, dramatically so in the last two decades. With this adjustment, the S&P 500 has been below trend since 2002. The current bear market has dropped the monthly average index price 50% below the trend, which puts us in the territory of those secular market troughs. In fact, this regression analysis, the closing low on November 20th came within 2% of the monthly average trough following the Crash of 1929.
So the question is . . .
Are you bearish or bullish about the market? Or for us data drudges, which is more reliable: the Bureau of Labor Statistics or www.ShadowStats.com?