net level premium

The chance of dying rises with age, so the true yearly cost of life insurance climbs every year — cheap at 30, expensive at 80. If insurers charged that rising cost directly, premiums would balloon just when older people can least afford them, and many would drop their cover. The net level premium is the fix: charge the same flat amount every year for the whole premium-paying period, like a fixed monthly gym fee that never changes even though you use the gym more in some years than others.

Precisely, the net level premium is the constant annual net premium P chosen so that the actuarial present value of all those equal payments equals the present value of the benefits (the equivalence principle), using only mortality and interest. Because it is flat, in the early years P is MORE than the true cost of that year's mortality, and in the later years it is LESS. The early overcharge is not lost — it is saved and accumulated to subsidize the later years. That accumulated, set-aside money is exactly the policy reserve. So 'level premiums' and 'reserves' are two sides of the same coin.

Level premiums are the standard for traditional whole-life and endowment policies, and they explain why such policies build cash value. They also create lapse-supported economics and the need for surrender values, because a policyholder who paid the early overcharges and then quits has prepaid future costs they will never use. A common misconception is that a level premium means a level cost of insurance; in truth the cost rises every year and the level premium just smooths the bill.