Skip to content

FRM Exam Part I · Learning From Financial Disasters

Financial Crisis of 2007-2009 and Securitization Explained

Updated 11 October 2026 · Fact-checked

The 2007-2009 crisis began with weak US subprime lending. Lenders sold loans into securitizations, passing credit risk to investors (originate-to-distribute), which weakened underwriting. Inflated ratings, high leverage, short-term funding in shadow banking and CDS exposures such as AIG's spread losses globally when house prices fell. Exam questions test the causal chain.

Understand Financial Crisis of 2007-2009 and Securitization

Start with a normal mortgage. A bank lends money to a home buyer and holds the loan. If the buyer defaults, the bank loses. So the bank has a reason to check the borrower carefully.

Securitization changes this. A bank pools many loans and sells them to a special purpose vehicle (SPV). The SPV issues bonds backed by the pool's cash flows. Bonds are sliced into tranches. Senior tranches are paid first and are rated highest. The equity or first-loss tranche absorbs losses first. This is the originate-to-distribute (OTD) model: the lender originates the loan and distributes the risk.

The problem was incentives. Originators earned fees on volume, not on loan quality. Once the loan was sold, they kept little of the default risk. Underwriting standards fell. Subprime loans, low-documentation loans and adjustable-rate loans with low teaser rates grew fast. The model relied on house prices continuing to rise so borrowers could refinance. When prices fell and teaser rates reset, defaults rose.

Rating agencies gave high ratings, often AAA, to senior tranches of mortgage-backed securities and to CDOs built from lower-rated tranches. Ratings relied on historical data and assumptions about low correlation of defaults across regions. Agencies were also paid by the issuers, which creates a conflict of interest. Investors leaned on ratings instead of doing their own analysis.

The losses spread through the shadow banking system: conduits, SIVs, investment banks and money market funds that performed bank-like maturity transformation without bank-like regulation or deposit insurance. They funded long-term assets with short-term borrowing such as asset-backed commercial paper and repo. When confidence fell, funding dried up and firms had to sell assets at falling prices. Leverage amplified losses. Insurers such as AIG had sold large amounts of credit protection through CDS on super-senior tranches. AIG did not hold enough capital or hedges, and it faced collateral calls as the values fell and its own rating was cut. This turned mark-to-market losses into a liquidity crisis.

Key formulas to remember

Tranche loss allocation
Losses hit tranches in order: equity (first loss) → mezzanine → senior
A tranche is only hurt once all junior tranches are exhausted. Attachment point is where a tranche starts to lose; detachment point is where it is wiped out.
Tranche thickness
Thickness = Detachment point − Attachment point
Thin mezzanine tranches are very sensitive to pool losses. Express as a % of the pool.
Loss to a tranche
Tranche loss = min(max(Pool loss − Attachment, 0), Detachment − Attachment)
Use pool loss in the same units as the attachment and detachment points (% of pool or currency).
Leverage ratio
Leverage = Total assets ÷ Equity
A fall in asset value of 1 ÷ leverage wipes out equity. At 30x, a 3.33% fall eliminates equity.

How to solve Financial Crisis of 2007-2009 and Securitization questions

Most questions on this topic ask for a cause, a mechanism or a failure. A few ask for a tranche loss calculation. Use this method.

  1. 1Identify the stage of the chain: lending, securitization, rating, funding, or contagion.
  2. 2Name the key mechanism: weak underwriting, misaligned incentives, rating error, leverage, maturity mismatch, or counterparty and collateral calls.
  3. 3Link the mechanism to a risk type: credit, liquidity, model, counterparty, or systemic.
  4. 4For a numerical question, write attachment and detachment points and the pool loss in the same units.
  5. 5Compute each tranche loss from the bottom up and check that the tranche losses add up to the pool loss.
  6. 6Eliminate options that overstate (say 'always' or 'only') or blame a single cause.
  7. 7Choose the option that matches the actual mechanism, not a plausible but wrong one.

Quickest way: Cause-and-mechanism matching

When to use it: Use for conceptual multiple-choice questions where you have to link a failure to its source.

  1. Ask who bore the credit risk after the loan was made. If it was passed on, think incentive problem.
  2. Ask what was funded short-term against long-term assets. If so, think run and liquidity risk.
  3. Ask whether a rating or model assumed low correlation. If so, think model risk.
  4. Ask whether collateral was posted on CDS. If so, think liquidity and counterparty risk.
  5. For tranche numbers, subtract the attachment point from the pool loss and cap the result at the tranche thickness.

Common mistakes in Financial Crisis of 2007-2009 and Securitization

  • Saying securitization itself caused the crisis.

    Textbook summaries compress the story into one word.

    Fix: State that the problem was the combination of weak incentives, opacity, ratings reliance and leverage, not the technique alone.

  • Thinking originators kept the credit risk.

    Students carry over the traditional bank model.

    Fix: In OTD, risk is transferred to investors. Lower retained risk led to weaker screening.

  • Treating AAA ratings as a measure of liquidity or price stability.

    Ratings are read as safety labels.

    Fix: A rating estimates credit risk only. Highly rated tranches still lost market value and liquidity when correlations and defaults rose.

  • Confusing shadow banks with regulated banks.

    Both borrow short and lend long.

    Fix: Shadow banks lacked deposit insurance, central bank access and comparable capital rules, so they were exposed to runs.

  • Describing AIG's loss as only default losses.

    Students think of CDS as plain insurance.

    Fix: Much of the strain came from collateral calls triggered by falling market values and AIG's downgrade, creating a liquidity crisis.

  • Applying tranche losses from the top down.

    Senior is listed first, so students allocate losses there.

    Fix: Losses hit the equity tranche first, then mezzanine, then senior.

Worked examples

Example 1

A securitization pool of $500 million has three tranches: equity 0%-5%, mezzanine 5%-15%, senior 15%-100%. The pool suffers a loss of 12% of its value. What is the dollar loss on the mezzanine tranche?

Show the solution
  1. Pool loss = 12% × $500 million = $60 million.
  2. Equity tranche: attachment 0%, detachment 5%, so it absorbs up to 5% × $500 million = $25 million. Pool loss exceeds this, so the equity loss is $25 million.
  3. Mezzanine attachment is 5%, detachment is 15%. Thickness = 10% × $500 million = $50 million.
  4. Pool loss above the attachment point = 12% − 5% = 7%, which is 7% × $500 million = $35 million.
  5. This is below the thickness of $50 million, so mezzanine loss = $35 million.
  6. Check: equity $25 million + mezzanine $35 million + senior $0 = $60 million.

Answer: $35 million (70% of the mezzanine tranche's value is lost).

Example 2

Which statement best explains why the originate-to-distribute model contributed to the growth of poor-quality subprime loans?
A. Originators held most loans to maturity, so they were overexposed to housing.
B. Originators earned fees on volume and passed credit risk to investors, so they had less reason to screen borrowers.
C. Rating agencies were barred from rating mortgage securities, so lenders ignored risk.
D. Regulators required lenders to offer subprime loans to all applicants.

Show the solution
  1. Recall the OTD logic: loans are made, pooled and sold.
  2. Option A describes the traditional model, not OTD, so reject it.
  3. Option C is false. Agencies rated these securities, and ratings were relied on heavily.
  4. Option D is not a description of how the model worked. It overstates regulation as the cause.
  5. Option B links fee income and risk transfer to weaker screening, which is the incentive problem.

Answer: B

Exam tips

  • Expect questions that ask you to match a cause to a risk type: incentives to credit risk, ratings to model risk, short-term funding to liquidity risk.
  • Watch for absolute words such as 'only' or 'always' in options. The crisis had several interacting causes.
  • For tranche questions, use the same units throughout and always check that tranche losses add to the pool loss.
  • Know AIG's story as a liquidity and collateral problem as well as a credit loss problem.
  • Keep the four-step chain in mind: lending, securitization and ratings, short-term funding and leverage, then contagion.

Practice questions from Learning From Financial Disasters

Financial Crisis of 2007-2009 and Securitization in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Financial Crisis of 2007-2009 and Securitization: frequently asked questions

What is the originate-to-distribute model?

It is a model in which a lender makes loans and then sells them, usually through securitization, rather than holding them. The credit risk moves to investors. It can weaken the originator's incentive to screen borrowers carefully.

What role did rating agencies play in the subprime crisis?

They gave high ratings to many senior tranches of mortgage securities and CDOs, based on models that assumed limited default correlation. Issuers paid for ratings, which created a conflict of interest. Investors relied on these ratings instead of doing their own analysis.

How did AIG's credit default swaps cause losses?

AIG sold protection on large amounts of structured credit through CDS without enough capital or hedging. As the securities' values fell and AIG was downgraded, it had to post large amounts of collateral. This created a liquidity crisis as well as credit losses.

What is shadow banking?

Shadow banking means bank-like credit and maturity transformation done outside the regulated deposit-taking system. Examples are conduits, SIVs and money market funds. It relied on short-term funding such as commercial paper and repo, so it was exposed to runs.