Anyone who is following the market on a daily basis is paying attention to the strength of the dollar versus other currencies. It can be confusing. While a strong dollar might seem like a good thing, there is actually an inverse market relationship with stocks -- at least in recent times.
I described the basics of the dollar debate here: Understanding the Debate on the Dollar. There are many opinions -- prescriptive, political, and descriptive. The next step is to consider some data.
Dollar Strength and U.S. Equity Market Returns
In my last article I highlighted the inverse relationship between a strong dollar and the stock market. This chart provides a dramatic illustration of the relationship for calendar 2009.
Sometimes a chart tells the story in a glance, but I always like to look at data as well. I used the Fed's measure of the dollar versus a broad basket of currencies, weighted by trade. The series started in 1995.
The correlation for this year is an almost perfect negative relationship: -.96.
A negative relationship sometimes stands out even more if you invert one of the scales. Here is that chart.
The data are the same, but the tight relationship is especially clear using the inverted scale.
So much for what we know. An obvious question for investors in stocks is what would happen if the dollar gets stronger. Perhaps we should look at more data.
A Longer Perspective
Some believe that a strong dollar is consistent with economic growth and a strong stock market. To examine this concept, we need to consider more data.
If we look at the full data series, we see long periods where dollar strength was consistent with a rising stock market. In fact, the correlation between the two series is a positive value: .35.
For an objective analyst of data, the chart suggests three conclusions:
- The relationship changes over time;
- The last year is quite atypical;
- There are other important variables at work.
The Carry Trade
The prevailing hypothesis about the dollar/stock relationship is the "carry trade." Supposedly there are investors/companies/speculators who are able to borrow in dollars at a very low interest rate. This makes the dollar the "funding currency." Most outspoken on this subject is Nouriel Roubini, who sees disaster ahead. [Full disclosure -- I am a contributor at Nouriel's valuable site. I respect and appreciate his encouragement of alternative viewpoints.]
The borrowers do not then do the obvious -- lend in another currency, hedging the difference with a forex trade. Instead they supposedly use the borrowed funds to engage in a variety of speculative trades -- emerging markets, real estate, and, of course, US stocks.
Following this logic, there is now a speculative bubble of major proportions. This seems implausible.
My skepticism comes partly from the lack of any real data supporting this viewpoint, and partly from the daily trading. If you really had this trade on, would you really take it off if the dollar moved by 0.4%? The carry trade hypothesis does not explain the closely calibrated trade between the dollar and stocks, but we see this every day.
For now, let us stick to conclusions supported by data. There is a strong inverse relationship. If you are a trader, you had better pay attention. If you are a long-term investor, you need to understand the long-term relationship.
Meanwhile, I invite reader comments, citations for new data, and fresh hypotheses. I will pursue this for at least one more article, considering various causal models.
