Large banks and dealers use and reuse collateral pledged by nonbanks, which helps lubricate the global financial system. The supply of collateral arises from specific investment strategies in the asset management complex, with the primary providers being hedge funds, pension funds, insurers, official sector accounts, money markets and others. Post-Lehman, there has been a significant decline in the source collateral for the large dealers that specialize in intermediating pledgeable collateral. Since collateral can be reused, the overall effect (i.e., reduced 'source' of collateral times the velocity of collateral) may have been a $4-5 trillion reduction in collateral. This decline in financial lubrication likely has impact on the conduct of global monetary policy. And recent regulations aimed at financial stability, focusing on building equity and reducing leverage at large banks/dealers, may also reduce financial lubrication in the nonbank/bank nexus.

and other colleagues at the IMF, as well as Hyun Song Shin, for very useful comments and discussions. Mr. Pozsar was a visiting scholar at the IMF during the time this Staff Discussion Note was prepared. The authors are grateful to Lindsay Mollineaux for excellent research assistance and to Helen Hwang for extensive editorial assistance on the paper. DISCLAIMER: This Staff DiscussionNote represents the views of the authors and does not necessarily represent IMF views or IMF policy. The views expressed herein should be attributed to the authors and not to the IMF, its Executive Board, or its management. Staff Discussion Notes are published to elicit comments and to further debate.

This Working Paper should not be reported as representing the views of the IMF.The views expressed in this Working Paper are those of the author(s) and do not necessarily represent those of the IMF or IMF policy. Working Papers describe research in progress by the author(s) and are published to elicit comments and to further debate.To mitigate systemic risk, some regulators have advocated the greater use of centralized counterparties (CCPs) to clear Over-The-Counter (OTC) derivatives trades. Regulators should be cognizant that large banks active in the OTC derivatives market do not hold collateral against all the positions in their trading book and the paper proves an estimate of this under-collateralization. Whatever collateral is held by banks is allowed to be rehypothecated (or re-used) to others. Since CCPs would require all positions to have collateral against them, off-loading a significant portion of OTC derivatives transactions to central counterparties (CCPs) would require large increases in posted collateral, possibly requiring large banks to raise more capital. These costs suggest that most large banks will be reluctant to offload their positions to CCPs, and the paper proposes an appropriate capital levy on remaining positions to encourage the transition.

This Working Paper should not be reported as representing the views of the IMF. The views expressed in this Working Paper are those of the author(s) and do not necessarily represent those of the IMF or IMF policy. Working Papers describe research in progress by the author(s) and are published to elicit comments and to further debate. This paper examines the sizable role of rehypothecation in the shadow banking system. Rehypothecation is the practice that allows collateral posted by, say, a hedge fund to its prime broker to be used again as collateral by that prime broker for its own funding. In the United Kingdom, such use of a customer's assets by a prime broker can be for an unlimited amount of the customer's assets while in the United States rehypothecation is capped. Incorporating estimates for rehypothecation (and the associated re-use of collateral) in the recent crisis indicates that the collapse in non-bank funding to banks was sizable. We show that the shadow banking system was at least 50 percent bigger than documented so far. We also provide estimates from the hedge fund industry for the "churning" factor or re-use of collateral. From a policy angle, supervisors of large banks that report on a global consolidated basis may need to enhance their understanding of the off-balance sheet funding that these banks receive via rehypothecation from other jurisdictions.

Between 1980 and before the recent crisis, the ratio of financial market debt to liquid assets rose exponentially in the U.S. (and in other financial markets), reflecting in part the greater use of securitized assets to collateralize borrowing. The subsequent crisis has reduced the pool of assets considered acceptable as collateral, resulting in a liquidity shortage. When trying to address this, policy makers will need to consider concepts of liquidity besides the traditional metric of excess bank reserves and do more than merely substitute central bank money for collateral that currently remains highly liquid.