Case Study 1 — The 2008 Shadow Banking Run: When Modern Finance Met Old-Fashioned Panic

The 2008 financial crisis was the most severe financial crisis since 1929. This case study walks through the mechanics of the shadow-banking run using the Diamond-Dybvig framework from §26.4, showing how a crisis that looked "modern" (mortgage-backed securities, credit default swaps, collateralized debt obligations) was actually a very old-fashioned phenomenon: a bank run.

The shadow banking system

By 2007, the U.S. financial system had two parallel banking systems:

Traditional banking: FDIC-insured commercial banks that took deposits, made loans, and were regulated by the Fed and other agencies. These banks were protected by deposit insurance and had access to the Fed's discount window (emergency lending).

Shadow banking: investment banks (Bear Stearns, Lehman Brothers, Goldman Sachs, Morgan Stanley, Merrill Lynch), money market funds, hedge funds, repo markets, and securitization vehicles. These entities performed banking functions — borrowing short-term and lending long-term — but were not regulated as banks and did not have FDIC insurance or Fed access.

The shadow banking system was enormous. By 2007, it was roughly the same size as the traditional banking system in total assets (~$10 trillion each). The maturity mismatch was severe: shadow banks funded themselves through overnight or very-short-term borrowing (repos, commercial paper) and invested in long-term, illiquid assets (mortgage-backed securities, CDOs).

The run

When housing prices started falling in 2007 and mortgage defaults rose:

Phase 1 (mid-2007): investors began to doubt the value of mortgage-backed securities. The credit rating downgrades started. Some hedge funds that were heavily invested in MBS failed (two Bear Stearns hedge funds in June 2007).

Phase 2 (late 2007 – early 2008): short-term funding markets tightened. Lenders in the repo market demanded more collateral and shorter terms. Some institutions found it harder to roll over their short-term debt. This was the equivalent of depositors starting to get nervous — not yet a run, but a reduction in trust.

Phase 3 (March 2008): Bear Stearns, the fifth-largest investment bank, faced a classic Diamond-Dybvig run. Its short-term creditors refused to roll over their lending. Bear couldn't liquidate its long-term assets fast enough to pay them. The Fed arranged a rescue: JPMorgan acquired Bear Stearns at $10/share (down from $170 a year earlier), with $30 billion in Fed guarantees.

Phase 4 (September 2008): Lehman Brothers, the fourth-largest investment bank, faced the same run. This time, the government chose not to rescue it. Lehman filed for bankruptcy on September 15, 2008 — the largest bankruptcy in U.S. history ($639 billion in assets).

Lehman's bankruptcy triggered the cascade: money market funds that held Lehman debt "broke the buck" (their net asset value fell below $1, triggering panic withdrawals). Repo markets froze (no one would lend overnight to anyone who might be the next Lehman). AIG faced massive CDS claims it couldn't pay. The entire short-term funding market — the circulatory system of modern finance — stopped functioning.

Phase 5 (September–October 2008): the government intervened massively. The Fed opened emergency lending facilities. The Treasury proposed TARP ($700 billion to buy toxic assets from banks). The FDIC temporarily guaranteed all bank deposits and money market funds. AIG was rescued with $182 billion in government support.

Why it was a bank run

The 2008 crisis had every feature of the Diamond-Dybvig bank run:

  1. Maturity mismatch: shadow banks funded long-term assets with short-term borrowing
  2. Self-fulfilling prophecy: creditors ran because they expected other creditors to run
  3. Coordination failure: the individually rational choice (withdraw your money) produced the collectively catastrophic outcome (the system collapsed)
  4. Contagion: one institution's failure (Bear Stearns) triggered runs on others (Lehman, AIG, money markets)

The key difference from a traditional bank run: there was no deposit insurance for shadow banking. FDIC protected traditional bank depositors (and traditional banks were mostly fine). Shadow banking creditors had no such protection — and they ran.

The lesson

The 2008 crisis demonstrated that deposit insurance and banking regulation are not just historical artifacts — they are essential infrastructure that prevents the financial system's inherent fragility from producing catastrophe. When the same fragility (maturity mismatch) existed outside the regulated system (shadow banking), the same catastrophe (bank run) occurred.

Post-crisis reforms (Dodd-Frank, the Volcker Rule, stress testing, higher capital requirements) have reduced — but not eliminated — the shadow banking system's vulnerability. The next crisis will likely involve a different part of the financial system, a different form of maturity mismatch, and a different trigger. But the underlying mechanism — the Diamond-Dybvig run — will be the same.

Discussion questions

  1. Why didn't the government rescue Lehman Brothers? Should it have? What were the consequences of letting Lehman fail?

  2. If FDIC insurance prevents runs on traditional banks, should similar insurance be extended to shadow banking? What would be the costs?

  3. "The 2008 crisis was caused by greed and deregulation." Apply the information-failure and bank-run frameworks. Was the crisis primarily about greed, about information, or about the structural fragility of the system?

  4. Could the 2008 crisis happen again? What has changed since then? What hasn't?

  5. The Fed acts as "lender of last resort" during a crisis. What is the moral hazard of this role?