The development and use of a model to estimate disability insurance exposure for a group of individuals to be underwritten for a coverage period is disclosed. The development of the model includes the use of medical claim data having a plurality % of medical claims made by a first model population having at least a respective plurality of first model population members and a disability insurance claim data having a plurality of disability insurance claims made by a second model population having at least a respective plurality of second model population members, which optionally may partially or wholly overlap with the first model population. A clinical medical condition classification system assigns corresponding medical condition causes to the disability insurance claims and the medical claims based on medical condition information.Development then categorizes the disability insurance claims and medical claims classified by medical condition, where each morbidity category comprises one or more medical conditions, to form a plurality of morbidity categories of disability insurance claims. Then, the proportions of the two types of claims are calculated for each morbidity category. Then, for each of the morbidity categories, a probability of having a disability claim during the coverage period is calculated using at least one conditional probability, the conditional probability being based on at least the proportion of disability insurance claims and the proportion of medical claims for each of the morbidity categories. From that, for each of the morbidity categories, an estimated the disability claim duration or cost is calculated.