Silly chart of the day, data-fitting edition

By Felix Salmon
August 29, 2009
Paul Kedrosky finds this chart in a Bloomberg story: it's the kind of thing which really reinforces one's belief in the wonders of data-fitting.

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Paul Kedrosky finds this chart in a Bloomberg story: it’s the kind of thing which really reinforces one’s belief in the wonders of data-fitting.

japangraph.jpg

The story isn’t actually particularly clear on exactly what the graph is showing, and specifically what “adjusted for currencies” means:

The Nikkei doubled between October 1998 and April 2000 in dollar terms, as the chart illustrates. The S&P 500 has risen 34 percent since March when the Dollar Index, a measure of the dollar against currencies in six major U.S. trading partners, is factored in.

So it seems that the BofA analysts who came up with this chart first converted the Nikkei to dollars, only to then convert the S&P 500, which was in dollars all along, out of dollars. Hm. And they chose pretty random start points: what makes 1980 in Japan analagous to 1990 in the US?

But the most breathtaking claim of all is right there in the Bloomberg headline: “S&P 500 May Surge 40% in Duplication of Japan”.

In other words, the people who came up with this chart are not saying that the US is going basically nowhere over the long term. Instead, they’re saying that there could be a big further rally in the S&P 500 over the short term. On the basis of the fact that the Nikkei rose sharply, in dollar terms, at the tail end of the last decade.

I feel quite safe in saying that of all the years to compare 2009-2010 to, 1999-2000 are probably not the most useful. And looking at what Japanese stocks did ten years ago will tell us absolutely nothing whatsoever about what US stocks are going to do now. No matter how many clever charts you come up with, or ridiculous justifications for the conclusions of your silly exercise in data-fitting:

“Even in economies overcoming credit booms, rallies can be powerful and last much longer than you think,” Bank of America’s Sadiq Currimbhoy, Arik Reiss and Jacky Tang wrote.

Well yes, if you’re caught up in the exuberant tail-end of a global stock-market bubble, maybe. But that spike in the yellow line that BofA thinks we might repeat on our orange line? Was basically a function of excesses like Softbank having a market capitalization of $200 billion. If you want to bet on that kind of thing happening in the US over the next year or two, feel free. But I’ll happily bet against you.

Update: Henry Blodget has the original Merrill report; it seems to admit how tortured the numbers it’s using are, and doesn’t go so far as to actually predict a 40% rally from these levels.

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