In summary, much information is available to help the employer identify which workers should receive safety and health information, education, and training and which workers should receive it before others. In addition, research has identified the following variables as being related to a disproportionate "share" of injuries and illnesses at the work site. 1. The age of the worker (younger employees have higher incidence rates of injury) 2. The length of time on the job (new employees have higher incidence rates) 3. The size of the firm (medium-size firms have higher incidence rates than smaller or larger firms) 4. The type of work performed (incidence and severity rates vary significantly by standard industrial classification [SIC] code) 5. The use of hazardous substances (by SIC code)