Financial Institutions and Banking

Bank Stress Tests – Two Approaches, Four Methods

Should you be stress testing your borrowers?
Most banks are familiar with the concept of stress testing: By evaluating the impact of adverse external events on a bank’s earnings, capital adequacy and other financial measures, stress testing can be a highly effective risk management tool. And while community banks generally aren’t required to conduct stress testing, banking regulators view it as a best practice.
For example, Office of the Comptroller of the Currency (OCC) guidance considers “some form of stress testing or sensitivity analysis of loan portfolios on at least an annual basis to be a key part of sound risk management for community banks.” Stress testing is often performed at the enterprise, or portfolio, level. However, testing at the individual loan level — beginning during the underwriting process — can be a powerful technique for revealing hidden risks.
Two approaches, four methods
Stress testing generally involves scenario analysis. This consists of applying historical or hypothetical scenarios to predict the financial impact of various events, such as a severe recession, loss of a major client or a localized economic downturn. Tools for performing such tests can range from simple spreadsheet programs to sophisticated computer models.
The OCC’s guidance doesn’t prescribe any particular methods of stress testing. It describes two basic approaches to stress testing: “bottom up” and “top down.” A bottom-up approach generally involves conducting stress tests at the individual loan level and aggregating the results. In contrast, a top-down approach applies estimated stress loss rates under various scenarios to pools of loans with similar risk characteristics.
The guidance outlines four methods to consider:
  1. Transaction level stress testing. This estimates potential losses at the loan level by assessing the impact of changing economic conditions on a borrower’s ability to service debt.
  2. Portfolio level stress testing. This method helps identify current and emerging loan portfolio risks and vulnerabilities (and their potential impact on earnings and capital) by assessing the impact of changing economic conditions on borrower performance, identifying credit concentrations and gauging the resulting change in overall portfolio credit quality.
  3. Enterprisewide stress testing. This considers various types of risk — such as credit risk within loan and security portfolios, counterparty credit risk, interest rate risk and liquidity risk — and their interrelated effects on the overall financial impact under a given economic scenario.
  4. Reverse stress testing. This approach assumes a specific adverse outcome, such as credit losses severe enough to result in failure to meet regulatory capital ratios. It then works backward to deduce the types of events that could produce such an outcome.
The right approach and method for a particular bank depends on its portfolio risk and complexity, as well as its resources. Even a simple stress-testing approach can produce positive results. (See “Canada’s mortgage stress-testing law.”)
Stress testing and the underwriting process
A bottom-up approach at the transaction level may offer a significant advantage: In addition to assessing the potential impact of various scenarios on a bank’s earnings and capital, it can, according to the OCC, help the bank “gauge a borrower’s vulnerability to default and loss, foster early problem loan identification and strategic decision making, and strengthen strategic decisions about key loans.”
For example, when evaluating a loan application, consider gathering information on the various risks the borrower faces — including operational, financial, compliance, strategic and reputational risks. This information can be used to run stress tests that measure the potential impact of various risk-related scenarios on the borrower’s ability to pay. An added benefit of this process is that, by discussing identified risks and stress test results with borrowers, you can help them understand their risks and develop strategies for managing and mitigating them, such as tightening internal controls, developing business continuity / disaster recovery plans or purchasing insurance.
A powerful tool
Stress testing is an important part of a community bank’s risk management process. It can also be a powerful tool for evaluating loan applications and revealing hidden vulnerabilities that may jeopardize potential borrowers’ ability to pay down the road. 
Sidebar: Canada’s mortgage stress-testing law
Canada takes an interesting approach to evaluating mortgage loans. Under a law that took effect in 2018, federally regulated banks are required to “stress test” all mortgage applicants. To pass the stress test, an applicant must qualify for a loan at the contractual interest rate plus 2% or at the Bank of Canada’s five-year benchmark rate (5.19% at press time), whichever is higher. So, for example, a borrower applying for a 3.75% mortgage would have to qualify for a mortgage at 5.75%. The rule doesn’t apply to borrowers who are renewing a mortgage with the same lender.
The idea behind the law is that requiring borrowers to qualify at a higher rate than they’re actually paying prevents them from overextending themselves. And since the law took effect, delinquency rates are down. But the law is also controversial because, among other things, it reduces purchasing power for many homebuyers and the benchmark rate is susceptible to manipulation by the largest banks. © 2020

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