How Collateral Reuse Can Turn Funding Stress into Systemic Risk
Summary
Rehypothecation occurs when a bank or broker reuses collateral pledged by a client to support its own borrowing or trading. The explanation describes how this practice can create a chain of claims: successive reuse makes the total collateral supporting the system much larger than the original assets. It calls the ratio of transformed collateral to original collateral the churn factor and cites a pre-Lehman example in which collateral expanded substantially through reuse.
The systemic danger arises when asset values fall and original collateral providers seek to prevent further reuse or recover their assets. Reduced collateral and a falling churn factor can shrink funding available across institutions, turning individual demands into a broader funding crisis. The discussion also flags valuation disputes and legal uncertainty, which can delay resolution when collateral is illiquid. It offers a conceptual account rather than a quantitative model, and its historical example reflects a specific period and legal setting; the mechanism’s severity depends on collateral terms, reuse limits, and institutional funding dependence.
Key ideas
- Rehypothecation is the reuse of client-posted collateral to support an intermediary’s own activity.
- Repeated reuse can make the collateral supporting claims exceed the original collateral base.
- The churn factor measures transformed collateral relative to original collateral.
- Falling asset values and demands to stop reuse can contract collateral and trigger widespread funding pressure.
- Illiquid collateral can add valuation disputes, legal uncertainty, and delays during stress.
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# How does rehypothecation cause systemic risk?
# How does rehypothecation cause systemic risk?
I've read in many places that rehypothecation causes systemic risk (not to be confused with systematic risk), but none offer an explanation. Is this because of the daisy-chain effect that would happen if a posted collateral to b who then posted it to c who then went into bankruptcy leaving A's original collateral tied up in bankruptcy proceedings?
## Answer by Bob Jansen (score 3)
https://quant.stackexchange.com/a/20745
With some help of Wikipedia I pieced together an answer, the meat is in this IMF paper.
First a definition:
> Re-hypothecation occurs when banks or broker-dealers re-use the collateral posted by clients such as hedge funds to back the broker's own trades and borrowing.
Indeed, a daisy chain involving enormous amounts was created before the Lehman collapse as in the UK it is possible to rehypotecate without limit which led to \$1 trillion of original collateral pledges to be transformed in \$4 trillion collateral. The ratio between the transformed collateral and the original factor has a name:
$$\textrm{Churn Factor} = \frac{\textrm{Transformed collateral}}{\textrm{Original collateral}}.$$
The paper agrees with the @experquisite's suggestion and because of the size of the outstanding collateral and the dependence of the banks on it for funding a real problem was created. In cases of stress systemic risk appears as follows:
Asset values went down because the bubble deflated. Furthermore, the original providers of the collateral demanded that their collateral was not reused by the bank so that their assets would not end up in bankruptcy proceedings. This leads to both a decrease in the original collateral and the churn factor greatly reducing the transformed collateral and thus to a funding crisis for all banks. A systemic crisis.
Also worth mentioning is that the valuation and legal issues surrounding this collateral can be messy resulting in uncertainty, delays and disputes. For example: two parties disagree about the value of assets (for which there is no liquid market (any more)) and both make claims on each other.Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.