Which of the following is NOT a factor in premium calculation for workers' compensation?

In the context of workers' compensation premium calculations, each factor plays a significant role in determining the overall cost of insurance. However, employee performance ratings are not typically used as a factor in this calculation.

The premium for workers' compensation insurance is primarily influenced by job class risk, which assesses the inherent risk associated with different job types, and industry classification, which groups companies into categories based on the risks presented by their operations. Payroll is also a critical factor, as premiums are often calculated based on the total payroll amount because higher payroll signifies more employees, which generally leads to increased risk.

Thus, while job class risk, payroll, and industry classification directly relate to the risk and financial exposure an insurer faces, employee performance ratings do not impact the assessment of risk for workers' compensation insurance purposes. This distinction highlights why performance ratings are not considered a factor in premium calculations.