How Lehman Brothers' $600B Collapse Triggered a Global Financial Crisis

By 2007, Lehman Brothers had $600B+ in assets and was the 4th-largest investment bank in the US. They had aggressively expanded into mortgage-backed securities (MBS) and collateralized debt obligations (CDOs), believing that real estate prices would continue rising.

The problem: their risk models assumed housing prices moved independently across regions. They didn't account for the possibility that ALL housing prices could decline simultaneously — which is exactly what happened.

What went wrong — No one mapped the Connection Circles:

A Connection Circles analysis of Lehman's position would have revealed devastating feedback loops:

• Lehman holds mortgage-backed securities → Housing prices decline → MBS values drop → Lehman's balance sheet weakens → Credit rating agencies downgrade Lehman → Counterparties demand more collateral → Lehman must sell assets at fire-sale prices → Asset sales push prices down further → MORE MBS values drop → Accelerating death spiral

This was a textbook Balancing Feedback Loop that had flipped into a destructive mode: the mechanism designed to balance risk (collateral requirements) actually accelerated the collapse.

What they needed — Pre-mortem thinking:

"Imagine Lehman has collapsed. Why?"

• Housing prices decline nationally (not just regionally)
• Our MBS portfolio is concentrated, not diversified
• When our credit rating drops, we face a liquidity crisis
• No one wants to buy our assets when everyone is selling

Each of these was not only possible but probable given the housing bubble indicators.

The Iceberg Model would have revealed:

• Events: Record housing prices, record MBS issuance
• Patterns: Housing prices disconnected from income levels, subprime lending increasing
• Structures: Incentive structures rewarded volume over quality; risk models assumed independence
• Mental model: "Housing prices always go up" — a belief contradicted by history

Lehman Brothers' bankruptcy was the largest in US history and triggered a global crisis:

• Filed for Chapter 11 bankruptcy on September 15, 2008 — $613B in debt
• Triggered a global financial crisis that wiped out $10 trillion in market value
• 26,000 employees lost their jobs
• Led to the Great Recession affecting hundreds of millions of people worldwide
• Resulted in massive government bailouts of other financial institutions

The contrast with JPMorgan Chase is instructive: Jamie Dimon had his team model extreme scenarios (a form of Pre-mortem thinking) and reduced JPMorgan's exposure to subprime mortgages early. JPMorgan not only survived but acquired Bear Stearns and Washington Mutual at distressed prices.