Accumulated benefit obligation (ABO): The actuary's estimate of the total retirement benefits (at their discounted present value) earned so far by employees, applying the pension formula using existing compensation levels.

Vested benefit obligation (VBO): The portion of the accumulated benefit obligation that plan participants are entitled to receive regardless of their continued employment.

Projected benefit obligation (PBO): The actuary's estimate of the total retirement benefits (at their discounted present value) earned so far by employees, applying the pension formula using estimated future compensation levels. (If the pension formula does not include future compensation levels, the PBO and the ABO are the same.