Peter, while, for a wide range of reasons, I have no doubt that there has been a credit crunch, it’s going to be a while (if ever) that its full extent can be accurately measured — and it’s going to be complicated. A sharp contraction in the commercial paper market may, for example, paradoxically increase bank lending, and you also have to look at questions such as the maturity of lending. If all that’s available (at a ‘reasonable’ price) is very short term money, that matters too, irrespective of the effect on the notional volume of lending.

Meanwhile there’s this from Paul Maidment at Forbes.com (my emphasis added):

What does a global credit crunch look like when it comes down to raw numbers? A 3% quarterly decline in international banking activity. It doesn’t sound like much, but it represents $1.1 trillion–and that was just a snapshot taken at the end of June, before the Lehman Bros. collapse worsened the crisis in interbank lending.
It is also three times bigger than the largest contractions of the past three decades–as long as such records have been kept. After the demise of hedge fund Long-Term Capital Management in 1998, international banking activity fell by 1.2% in the fourth quarter of that year. After the dot-com bubble burst, the contraction was 1%, or $125 billion–chump change compared with today’s banking volumes.
The numbers come from the provisional international banking statistics for the second quarter of this year, released Thursday by the Bank for International Settlements, the Basel, Switzerland-based organization that acts as a lender for central banks. BIS says most of the decline was accounted for by “short-term interbank credits in U.S. dollars,” i.e., banks not lending to each other overnight–the logjam in credit markets we have heard so much about being at the heart of the credit crunch.
In contrast, the BIS notes, lending in emerging markets, particularly developing Europe, and within the euro area, continued to grow. Not necessarily a happy sign as it includes German bank lending to troubled Iceland. The BIS numbers show German banks lent far more to the crisis-stricken island than British banks.