In talking about the fact that Manufacturing as a percentage of GDP O'Brien notes that manufacturing has dropped from being over 25% of GDP to just under 13% of GDP since 1947. He notes that in the same time frame the financial sector went from around 10% to around 20%. He even includes a nice graph.
I don't know if O'Brien added the text to the graph, but if he did he is deliberately being misleading (and if he didn't he wasn't studious enough to review the graphic before using it.)
Here are a few problems, first what they call "Financial Sector" in the large text is actually listed in the legend of the graph as "Finance, insurance, real estate, rental, and leasing. It is FAR MORE than just the finance department. Also, the text at the bottom says "Most sectors stayed nearly the same" and this is a total lie. The problem with this graph is that it places a lot of lines at the bottom close together and while some of the lines do remain close to the same there are other lines that grow almost as much as the "Finance" line, namely Professional and Business Services and Educational services, Healthcare, and Social Assistance. And at the same time you also notice large decreases in agriculture and mining.
In fact - when you clear up the "noise" the graph looks completely different.
Why does someone do things like this? Because they can't make their argument without misleading people. Yes, far less of our GDP is made in manufacturing, but it still accounts for the third highest part of our economy. In fact, this chart had to lump Finance, Insurance, Real Estate, Rental, and Leasing all together in order to make it appear to contribute more to the economy. If O'Brien wants to make the case that we need to refocus our economy or that we should distrust Wall Street that is fine, but by using this graphic his intent is now to mislead people - and that is unforgivable.