What is the difference between q_x and mu_x in actuarial notation?

q_x is the probability of dying between exact ages x and x+1 (discrete). mu_x (force of mortality) is the instantaneous hazard rate at exact age x (continuous). They are related by q_x = 1 - exp(-integral of mu from x to x+1). Both are derived from the same underlying mortality experience.

Why does fractional age interpolation matter?

When calculating annuity factors or policy reserves at non-integer ages (e.g., age 45.7), interpolation between integer-age q values is needed. UDD assumes deaths spread uniformly within the year; constant force assumes a constant hazard. UDD is simpler; constant force is more consistent with continuous-time models.

q-Rate from Life Table Interpolation

Interpolate age-specific mortality rate (q_x) from actuarial life tables between integer ages using uniform distribution of deaths (UDD) or constant force of mortality assumption.

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Frequently Asked Questions

What is the difference between q_x and mu_x in actuarial notation?

Why does fractional age interpolation matter?