What is ordinarily the measure of pension expense when an enterprise fund sponsors a single-employer defined benefit plan?

The measure of pension expense for an enterprise fund sponsoring a single-employer defined benefit plan is typically the actuarially determined annual required contribution. This amount is calculated based on various factors including projected future benefit payments, current funding levels, demographic assumptions, and investment return expectations.

This measure is significant because it encompasses not only the actual contributions made during the period but also reflects the long-term obligations of the plan. The actuarial assessment ensures that the contributions are sufficient to cover both past service and future benefit commitments while aligning the funding strategy with the overall financial health of the entity sponsoring the plan. Thus, it delivers a comprehensive insight into the financial commitment an organization has towards its employees' retirement benefits.

Other options, such as contractually required contributions, actual contributions, and related benefit payments, do not provide the same thorough view of the pension liabilities and the expense recognized on the funding schedule, making the actuarially determined annual required contribution the most accurate measure of pension expense.