Some very interesting work has been done on this in recent times, including by Manmohan Singh and Zoltan Pozsar at the IMF, along with James Aitken.1 Hyun Shin and others have developed a useful framework in which to think about the issue.2 The evidence seems to be that there is a sizeable reduction in the velocity of collateral taking place.
Some of this is because of a change in the willingness to lend securities on the part of some asset managers, some is a function of regulatory changes. This has implications for the provision of credit, particularly from the shadow banking sector. It is an area which is certainly worth examining in more detail.