Wednesday, January 21, 2009

JP Morgan here made the unforgivable error of making the diameter, not the area, of the circles correspond to the market capitalization.

This controversy makes me laugh. From Felix Salmon:

"
Bank Capitalization Chart of the Day
bankchart2small.jpg

Here are the capitalizations of the biggest banks in the world: the blue circles dark blue bars correspond to how much they were worth in the second quarter of 2007, while the green circles light blue bars are the capitalizations as of yesterday. (I've updated the chart since this blog entry was first posted; see below for details.) The second circle from the left on the top row (RBS) does honestly have a tiny green circle -- it's just hard to see at this scale. Click for a bigger version.

Update: Alphaville had this earlier, and says that JP Morgan might be fudging things a little.

Update 2: Oh dear, my commenters are right and I am blind: JP Morgan here made the unforgivable error of making the diameter, not the area, of the circles correspond to the market capitalization. I've replaced the chart with a much better one from Matthew Turner. Apologies to all, and many thanks to Matt."

The only use of either of these graphs is just to visually represent the fact that banks have fallen in value. Other than that, it's useless. You would have to analyze each business separately to understand why each business is where it is in comparison with the others. A comparative graph is worthless without a comparative analysis. Any chart or graph needs to be judged by its use. The only use of this chart is amusement. Spending time getting the perfect representation means that people were actually under the opinion that this comparative graph was in some way meaningful. It isn't.

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