existing damages. Detecting insurance fraud The detection of insurance fraud generally occurs in two steps. The first step is to identify suspicious claims that have a higher possibility of being fraudulent. This can be done by computerized statistical analysis or by referrals from claims adjusters or insurance agents. Additionally, the public can provide tips to insurance companies, law enforcement and other organizations regarding suspected, observed, or admitted insurance fraud perpetrated by other individuals. Regardless of the source, the next step is to refer these claims to investigators for further analysis. Due to the sheer number of claims submitted each day, it would be far too expensive for insurance companies to have employees check each claim for symptoms of fraud. Instead, many companies use computers and statistical analysis to identify suspicious claims for further investigation. There are two main types of statistical analysis tools used: supervised and unsupervised. In both cases, suspicious claims are identified by comparing data about the claim to expected values. The main difference between the two methods is how the expected values are derived. In a supervised method, expected values are obtained by analyzing records of both fraudulent and non-fraudulent claims. According to Richard J. Bolton and David B. Hand, both of Imperial College in London, this method has some drawbacks as it requires absolute certainty that those claims analyzed are actually either fraudulent or non-fraudulent, and because it can only be used to detect types of fraud that have been committed and identified before. Unsupervised methods of statistical detection, on the other hand, involve detecting claims that are abnormal. Both claims adjusters and computers can also be trained to identify "red flags", or symptoms that in the past have often been associated with fraudulent claims. Statistical detection does not prove that claims are fraudulent; it merely identifies suspicious claims that must be investigated further. Fraudulent claims can be one of two types: they can be otherwise legitimate claims that are exaggerated or "built up", or they can be false claims in which the damages claimed never actually occurred. Once a built up claim is identified, insurance companies usually try to negotiate the claim down to the appropriate amount. Suspicious claims can also be submitted to "special investigative units", or SIUs, for further investigation. These units generally consist of experienced claims adjusters with special training in investigating fraudulent claims. These investigators look for certain symptoms associated with