Investment banks and financial crisis 2007-2008

Leverage ratios of investment banks (from Wikipedia)

US Gross Federal Debt, unadjusted for inflation (from Wikipedia)

If we want to try to understand the global financial crisis going on now, we need to try to understand the role of investment banks in USA.
There is an interesting paper about investment banks, the paper was written and it's called
The Demise of Investment-Banking Partnerships: Theory and Evidence
written in 2004 by Alan D. Morrison (University of Oxford-Said Business School; University of Oxford-Merton College) and William J. Wilhelm Jr (University of Oxford-Said Business School; University of Virginia-School of Law)

Abstract:
Until 1970, the New York Stock Exchange prohibited public incorporation of member firms. After the rules were relaxed to allow joint stock firm membership, investment-banking concerns organized as partnerships or closely-held private corporations went public in waves, with Goldman Sachs (1999) the last of the bulge bracket banks to float. In this paper, we ask why the Investment Banks chose to float after 1970, and why they did so in waves. In our model, partnerships have a role in fostering the formation of human capital. We examine in this context the effect of technological innovations which serve to replace or to undermine the role of the human capitalist and hence we provide a technological theory of the partnership's going-public decision. We support our theory with a new dataset of investment bank partnership statistics.

This is a very important issue: before 1970, the New York Stock Exchange (the famous Wall Street) prohibited investment banks from going public (in USA "going public" means starting an IPO in order to enter the stock exchange).

We can read from the official site of NYSE:

Public Can Own Member Firms
March 26 1970
Public ownership of member firms is approved for the first time

And, maybe, it was the beginning of the end...

James Surowiecki wrote (29 September 2008; The New Yorker):

[...] All, then, seemed good. But, for Wall Street firms, going public was a deal with the devil, because it meant exposing themselves to what was, in effect, a minute-by-minute referendum, in the form of the stock price, on the health of their operations. This was fine as long as things were going well—the higher the stock price, the richer everyone got—but, once things started to go bad, that market referendum started to look like a vote of no confidence. And that made the problems that the companies were already facing much, much worse. [...]

and

[...] All companies, of course, worry about how their stock is doing. But for most the stock price is a product of performance, rather than a cause of it. If Procter & Gamble’s stock plummeted tomorrow, people would still keep buying Tide. By contrast, if an investment bank’s share price tumbles, it not only wrecks people’s confidence but also can lead to credit-rating downgrades, which provoke a further decline in the stock price, and so on. The downward spiral can be stunningly fast and near-impossible to escape. [...]

After 1970, investment banks could enter the stock exchange, and theese are the dates when they decided to do so (NYSE):

1971 Merrill Lynch
1985 Bear Stearns
1986 Morgan Stanley
1994 Lehman Brothers
1999 Goldman Sachs

What happened to the 5 investment banks that we can see from the first image?

Merrill Lynch: acquired by Bank of America
Bear Stearns: acquired by JPMorgan Chase (with the help of the Fed)
Morgan Stanley: changed its status from investment bank to bank holding
company
Lehman Brothers: bankruptcy
Goldman Sachs: changed its status from investment bank to bank holding
company

On 23rd September 2008 we heard:

The FBI is investigating Fannie Mae, Freddie Mac, Lehman Brothers Holdings Inc and insurer American International Group Inc and their senior executives for potential mortgage fraud, CNN reported on Tuesday.

Well, who is going to investigate the role of the Sec about the subprime crisis??