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Systemic Risk & Stabilityintermediate

Financial Contagion

Contagion is the transmission of distress from one institution or market to others through the financial network. Two channels matter. Direct (counterparty) contagion runs along contractual links: if A defaults, its creditors B and C take losses and may default in turn (a domino chain). Indirect (information and price) contagion runs through common exposures and behavior: bad news about A causes investors to flee similar firms or to run on funding, and shared assets get marked down for everyone. Interconnectedness raises both channels. The same linkages that diversify small shocks can propagate large ones, so network density cuts both ways.

Why it matters

Contagion is finance catching a cold. The direct channel is literal contact: you owe me, you fail, now I am short the cash and might fail too. The indirect channel is fear: people see one bank wobble and assume the next one like it is sick, so they pull their money and sell its assets, making the sickness real. Dense interconnection is a double-edged sword. In calm times it spreads risk thinly; in a crisis it becomes the wiring that carries the shock to everyone.

Formulas

Counterparty loss propagation
Lossj=∑i∈defaultsLGDij ⋅ Exposureij\text{Loss}_j = \sum_{i \in \text{defaults}} \text{LGD}_{ij}\,\cdot\,\text{Exposure}_{ij}
Bank jj’s direct contagion loss aggregates exposures to each defaulting counterparty ii times loss-given-default. If this loss exhausts jj’s capital, jj also defaults and the cascade continues.

Worked examples

Scenario

After Lehman defaulted in 2008, the Reserve Primary money-market fund "broke the buck." Trace the contagion channels.

Solution

Direct: the fund held Lehman commercial paper, so Lehman’s default imposed a direct counterparty loss that pushed its net asset value below $1. Indirect: investors, fearing other funds held similar paper, ran on prime money funds broadly, forcing a fire sale of commercial paper and freezing short-term corporate funding. One default propagated through both contractual links and panic.

Scenario

In March 2023, Silicon Valley Bank (about $209 billion in assets) failed on 10 March and Signature Bank (about $110 billion) was closed on 12 March, followed within days by runs on other regional banks with similar deposit and bond profiles. Which channel dominated?

Solution

Primarily indirect contagion. Many threatened banks had little direct exposure to SVB, but depositors inferred that banks with comparable uninsured-deposit and held-to-maturity-bond profiles were vulnerable and withdrew funds. Information and behavior, amplified by social media and mobile banking, carried the shock more than contractual dominoes did. The scare crossed borders within a week: by 19 March the Swiss authorities brokered UBS’s emergency takeover of Credit Suisse, a global systemically important bank, to halt a separate loss of confidence.

Common mistakes

  • ✗Contagion only spreads through direct counterparty exposures. Indirect contagion through common exposures, fire sales, and panic-driven runs is often the larger channel, even between firms with no contracts between them.
  • ✗More interconnection always makes the system safer by spreading risk. Interconnection diversifies small shocks but propagates large ones; beyond a point, density turns the network into a transmission system for crises.
  • ✗Contagion requires the first firm to be insolvent. A mere loss of confidence or a liquidity freeze can transmit distress even to solvent firms, through runs and the drying-up of funding.

Revision bullets

  • •Contagion: transmission of distress across the financial network
  • •Direct channel: counterparty defaults cascade along contractual links
  • •Indirect channel: common exposures, fire sales, and panic-driven runs
  • •Interconnectedness diversifies small shocks but propagates large ones
  • •Confidence loss can spread even to solvent firms

Quick check

Indirect (information) contagion differs from direct (counterparty) contagion because it

Why is dense interconnection described as "double-edged" for systemic risk?

Connected topics

Systemic RiskProcyclicalityFire SalesSIFIs / TBTF

Sources

  1. Allen & Gale (2000)
    Allen, F., and Gale, D. "Financial Contagion." Journal of Political Economy 108 (1), 2000, 1-33.
    Foundational model of contagion through the interbank network structure.
  2. Acharya, Engle & Richardson (2012)
    Acharya, V. V., Engle, R., and Richardson, M. "Capital Shortfall: A New Approach to Ranking and Regulating Systemic Risk." American Economic Review: Papers & Proceedings 102 (3), 2012, 59-64.
    Links interconnected capital shortfalls to systemic spillovers; motivates SRISK.
  3. BCBS (2023)
    Basel Committee on Banking Supervision. Report on the 2023 Banking Turmoil. Bank for International Settlements, October 2023.
    Official analysis of the March 2023 turmoil (SVB, Signature, Credit Suisse); documents how social media and digital banking accelerated deposit runs.
How to cite this page
Dr. Phil's Quant Lab. (2026). Financial Contagion. Derivatives Atlas. https://phucnguyenvan.com/concept/frm-contagion
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