non so rispondere alla tua domanda, ma ricordo che uno dei primi commenti sul leverage è stato di Zingales (è italianissimo...)
nel corso della sua testimonianza:
The demise of Lehman Brothers is the result of its very aggressive
leverage policy in the context of a major financial crisis.
In the case of Lehman (and other investment banks), this problem was
aggravated by two factors: the extremely high level of leverage (asset-to equity
ratio) and the strong reliance on short-term debt financing. While
commercial banks cannot leverage their equity more than 15 to 1, Lehman
had a leverage of more than 30 to 1. With this leverage, a mere 3.3% drop
in the value of assets wipes out the entire value of equity and makes the
company insolvent.
In turn, the instability created by the leverage problem was
exacerbated by Lehman’s large use of short-term debt. Reliance on short term
increases the risk of “runs” similar to the ones bank face when they are
rumored to be insolvent.
It is important to note that Lehman did not find itself in that situation by
accident; it was the unlucky draw of a consciously-made gamble.
testo ocmpleto, che include anche commenti sulle agenzie di rating:
IL SOLE 24 ORE
Second, the massive amount of issuance made by a limited number of
players (of which Lehman was one) changed the fundamental nature of the
relationship between credit rating agencies and the investment banks issuing
these securities. In their sample of 1,257 mortgage securitization deals
Nadauld and Sherlund (2008) find that Lehman alone had 128 deals.
In the past each customer, issuing only a couple of securities, had no
market power over the rating agencies. With the diffusion of collateralized
debt obligations, the major investment banks were purchasing hundreds of
rating services a year. As a result, instead of submitting an issue to the rating
agency’s judgment, investment banks shopped around for the best ratings
and even received manuals on how to produce the riskiest security that
qualified for a AAA rating. For example, the Standard & Poor’s website
used to provide a CDO Evaluator Manual (Benmelech and Dlugoszb, 2008).
The CDO Evaluator is an optimization tool that enables issuers to achieve
the highest possible credit rating at the lowest possible cost.