Anyone who works in a field as esoteric as catastrophe risk management knows the feeling of being at a cocktail party and having to explain what you do.

So what is catastrophe modeling anyway?

Catastrophe modeling allows insurers and reinsurers, financial institutions, corporations, and public agencies to evaluate and manage catastrophe risk from perils ranging from earthquakes and hurricanes to terrorism and pandemics.

Just because an event hasn’t occurred in that past doesn’t mean it can’t or won’t. A combination of science, technology, engineering knowledge, and statistical data is used to simulate the impacts of natural and manmade perils in terms of damage and loss. Through catastrophe modeling, RMS uses computing power to fill the gaps left in historical experience.

Models operate in two ways: probabilistically, to estimate the range of potential catastrophes and their corresponding losses, and deterministically, to estimate the losses from a single hypothetical or historical catastrophe.

**Catastrophe Modeling: Four Modules**

The basic framework for a catastrophe model consists of four components:

**The****Event Module**incorporates data to generate thousands of stochastic, or representative, catastrophic events. Each kind of catastrophe has a method for calculating potential damages taking into account history, geography, geology, and, in cases such as terrorism, psychology.

**The Hazard Module**determines the level of physical hazard the simulated events would cause to a specific geographical area-at-risk, which affects the strength of the damage.

**The Vulnerability Module**assesses the degree to which structures, their contents, and other insured properties are likely to be damaged by the hazard. Because of the inherent uncertainty in how buildings respond to hazards, damage is described as an average. The vulnerability module offers unique damage curves for different areas, accounting for local architectural styles and building codes.

**The Financial Module**translates the expected physical damage into monetary loss; it takes the damage to a building and its contents and estimates who is responsible for paying. The results of that determination are then interpreted by the model user and applied to business decisions.

**Analyzing the Data**

Loss data, the output of the models, can then be queried to arrive at a wide variety of metrics, including:

**Exceedance Probability (EP):**EP is the probability that a loss will exceed a certain amount in a year. It is displayed as a curve, to illustrate the probability of exceeding a range of losses, with the losses (often in millions) running along the X-axis, and the exceedance probability running along the Y-axis.

**Return Period Loss:**Return periods provide another way to express exceedance probability. Rather than describing the probability of exceeding a given amount in a*single*year, return periods describe how*many*years might pass between times when such an amount might be exceeded. For example, a .4% probability of exceeding a loss amount in a year corresponds to a probability of exceeding that loss once every 250 years, or “a 250-year return period loss.”

**Annual Average Loss (AAL):**AAL is the average loss of all modeled events, weighted by their probability of annual occurrence. In an EP curve, AAL corresponds to the area underneath the curve, or the average expected losses that do not exceed the norm. Because of this, the AAL of two EP curves can be compared visually. AAL is additive, so it can be calculated based on a single damage curve, a group of damage curves, or the entire event set for a sub-peril or peril. It also provides a useful, normalized metric for comparing the risks of two or more perils, despite the fact that peril hazards are quantified using different metrics.

**Coefficient of Variation (CV):**The CV measures the size, or degree of variation, of each set of damage outcomes estimated in the vulnerability module. This is important because damage estimates with high variation, and therefore a high CV, will be more volatile than an estimate with a low CV. More often than not, a property will “behave” unexpectedly in the face of a given peril, if the property’s characteristics were modeled with high volatility data versus a data set with more predictable variation. Mathematically, the CV is the ratio of the standard deviation of the losses (or the “breadth” of variation in a set of possible damage outcomes) over the mean (or average) of the possible losses.

Catastrophe modeling is just one important component of a risk management strategy. Analysts use a blend of information to get the most complete picture possible so that insurance companies can determine how much loss they could sustain over a period of time, how to price products to balance market needs and potential costs, and how much risk they should transfer to reinsurance companies.

Catastrophe modeling allows the world to predict and mitigate damage resulting from the events. As models improve, so hopefully will our ability to face these catastrophes and minimize the negative effects in an efficient and less costly way.