The Basics

Noise Trading

One of the more interesting topics I’ve come across in my delving into research in the area of Behavioral Finance is the term “noise trader”. I’ve been reading a paper on the subject which has former Treasury Secretary Larry Summers as one of the co-authors. To put it simply, noise traders are those who do not operate on a strictly rationale valuation basis when making buy/sell decisions in the market. In other words, if you’re reading this blog post you are almost certainly a noise trader in the way academia defines the term.

One of the things I find interesting is how Summer & Co. refer to the non-noise set of market participants as “sophisticated investors”. The implication is that these folks can build a proper valuation model with the correct inputs that correctly account for risk. The implication is that noise traders can’t correctly estimate future risk (among other things), while the so-called sophisticated investors never makes any errors in estimating all the contributing factors which go into a valuation calcuation. Not very realistic in a world of failable human actors, in the latter case, or in terms of valuing the abilities of some very smart researchers on the other.

What’s kind of funny is the expressed observation of the paper that noise traders make value investing a sub-optimal course. One the one side, noise traders are said to increase volatility, and thus risk, reducing asset prices (stocks, really) in terms of their attractiveness to the non-noise set. On the other side, the added volatility actually increases the returns accruing to a noise trading approach. I think a lot of traders will feel vindicated in this. 🙂

I haven’t gotten all the way through the paper, and there’s a lot of very academic stuff, so it’s not the easiest read in the world. For those with an inclination, though, it’s an interesting bit of intellectual discourse.

The Basics

Influences on Price/Earnings Ratios

The Price/Earnings ratio (P/E) is a metric commonly used in fundamental analysis of stocks – both individually and in terms of indices. It can be a useful gauge of relative over- or under-valuation both in terms of looking at a stock or index singularly, or in comparison with others. For example, one could evaluate where the current P/E of JPM is in terms of it’s historical levels and/or in terms of how it compares to BAC, C, WFC, and others in the banking sector.

It’s not recommended that P/E be used in isolation – meaning low P/E = cheap stock, or vice versa. There are reasons why a P/E can be low or high, including changing expectations for growth rates which have not necessarily started showing up in the earning data. For that reason, you should only use the P/E in conjunction with other forms of analysis.

Looking at Stock Valuation Math
In thinking about doing so, it’s worth noting the two mathematical influences on the P/E ratio when looking at the valuation of a stock. They are the earnings growth rate and the interest rate. Stock valuations are done by determining what future earnings are expected to be, then discounting them back to the present by doing a Present Value (PV) calculation.

Earnings growth rate assumptions obviously factor into the expectations for future annual earnings per share figures. The table below shows the impact of different levels of growth rate expectations for earnings on valuation, and thus P/E.

The above calculations only go out to 5 years. Valuations are often done with an additional perpetual growth rate for the years beyond #5. For the purposes here, however, five years is enough to make the point.

Notice in the yellow Value row how the valuation of the stock in question (based on adding the PVs of the earnings forecasts for Years 1 through 5) rises as the assumed annual growth rate (left column) goes from 0% up to 20%. Using the Year 0 earnings (current year achieved result) as the E in the P/E, and the valuation as the P, we get the P/E listed in the right-most column. Notice how it rises in line with rising growth rates.

Now, this probably won’t come as a big surprise. It’s commonly understood that higher earnings growth rates translate to higher P/Es. That’s why the P/E of a perceived growth stock will generally be higher than the P/E of a more mature stock, like a utility. It also should be noted, however, that P/Es also vary because of interest rates. The discounting of future earning’s done in the valuation process employs an interest rate to calculate the PVs. Thus, interest rates impact P/Es.

The chart below provides an example.

The chart above shows the P/E value of a stock with a 5% annualized earnings growth rate with valuations determined using discount rates from 1% to 10th. Notice the steady decline as interest rates rise. It’s not a big change, of course. Changes in earnings growth rates are more impactful. This may be something very important for the stock market moving forward, however. If we think interest rates are going to be rising in the years ahead, then we have to factor in slightly lower P/E ratios.