I'm not really sure if there's much relevance to the financial sector's weight in the S&P500, as all it tells us is that yes it was a lot higher a few years back. Which is something we all know. Will it continue to drop? Should it be higher? I don't think the relative size of the finance sector will matter either way.
The relative size of the circles does not reflect the numbers inside the circles, which makes this diagram blow things way out of proportion.
Yes. An accurate comparison requires a simple bar chart. Apparently, the genius behind the graph didn't pass 8th grade math. You don't add diameters to calculate the volume of a circle. Using Citi as an example, 225 of the small green circles are needed to fill the big blue circle. Last time I checked 255bil isn't 225 times larger than 19bil.