I wrote a post last November in which I argued that the S&P 500 was undervalued. Since then, the S&P 500 has risen 5.16%, from about 1220 to 1283. This is a pretty good gain, but I think that the S&P 500 has further to go. Relative to bonds, the S&P 500 is still undervalued and due for more gains.
According to Standard & Poor's, the projected reported earnings through 12/31/06 for the sum of the components of the S&P 500 is about $79.30/share. As discussed above, the S&P 500 index currently trades at about 1283. Accordingly, the forward P/E ratio of the S&P 500 index is about 16.18 (1283/$79.30). This is slightly higher than the historical P/E ratio of around 14-15. However, bonds are much more richly valued than their historical averages. Moreover, other asset classes such as real estate and commodities are also richly valued right now. It therefore seems inevitable that stocks will eventually catch up to the performance of these other asset classes.
Stocks have been weighed down over the past year in large part due to high energy prices and a FED that has been steadily raising short-term interest rates. However, consumer price inflation is still relatively low and bonds are expensive. The yield on the 10-yr US bond is currently about 4.56%. The earnings yield on the S&P 500 based on estimated 2006 earnings is about 6.18% (i.e., the inverse of the 16.18 P/E ratio). Therefore the earnings yield on the S&P 500 is about 1.62% higher than the 10-yr bond yield. This is large disparity and is certain to shrink over the next few years as the S&P 500 outperforms the 10-yr bond.
I believe that 2006 will continue to be a good year for the S&P 500. The S&P 500 probably won't increase in value every month, but even after accounting for a pullback or two this should be a good year nevertheless.