3.2 How Life Insurance Works: Mortality, Interest, Reserves

Life insurance works by pooling risk. Many policyholders pay premiums into a common fund; because only a predictable fraction of them die in any year, the fund can pay large death benefits to the beneficiaries of those who die while staying solvent. To set premiums and stay financially sound, insurers rely on three actuarial pillars: mortality, interest, and expenses, and they must hold reserves to guarantee future claims. This section explains each pillar and how it shapes the premium and the reserve.

Mortality — The Cost of Dying

Mortality is the rate at which insured people are expected to die at each age. Insurers measure it with a mortality table (also called an actuarial or life table), which is built from large population studies and shows, for each age, the probability of dying within the next year.

The U.S. standard is the Commissioners Standard Ordinary (CSO) Mortality Table; the 2017 CSO is the current version and reflects longer life expectancy. The CSO table sets the minimum reserve an insurer must hold. The portion of premium that pays for pure death-benefit cost is the mortality charge — it rises with age because the probability of death rises with age.

The Three Factors That Determine Premium

Every premium is built from three components. Two raise the premium and one lowers it.

The interest assumption is the most counter-intuitive item on the exam: a higher assumed interest rate produces a lower premium because the insurer expects investment income to fund part of the future benefit. Memorize: mortality up = premium up; interest up = premium down; expenses up = premium up.

Exam Tip: A "gross premium" equals the "net premium" (mortality and interest) plus the expense loading. The net premium ignores expenses.

Net Single, Net Level, and Gross Premium

Actuaries first compute a net single premium (NSP) — the lump sum, payable today, that exactly funds the future death benefit using only mortality and interest. Because few buyers pay a single lump sum, the NSP is converted into a net level premium, an equal annual amount payable over the premium-paying period. Adding the expense loading to the net level premium produces the gross premium the client actually pays.

Simplified illustration: Suppose a one-year term benefit of $100,000 covers a group whose mortality table predicts 5 deaths per 1,000 insureds that year. The pure mortality cost spread across 1,000 insureds is:

• Total expected claims = 5 × $100,000 = $500,000
• Cost per insured (ignoring interest) = $500,000 ÷ 1,000 = $500

If the insurer can earn interest on premiums collected at the start of the year, the required premium drops below $500. After adding expense loading of, say, $40, the gross premium might be about $520. This shows all three factors at work in one number.

Reserves — The Insurer's Promise to Pay

A reserve (specifically the legal or statutory reserve) is a liability the insurer must carry on its books equal to the present value of future benefits minus the present value of future net premiums. Reserves exist because level premiums overcharge in early years and undercharge in later years: in the early years the level premium exceeds the true mortality cost, and the insurer sets the excess aside, with interest, to cover the later years when mortality cost exceeds the premium.

Key points the exam tests:

• Reserves are a liability, not the insurer's profit.
• The CSO table and a statutory interest rate set the minimum reserve.
• Reserves vs. cash value: the reserve is the insurer's accounting liability; the cash value is the living benefit the policyowner can access. They are related but not identical — cash value is generally lower in early years because of surrender charges and expense recovery.
• Strong reserves keep the insurer solvent and able to pay claims decades into the future.

Participating vs. Nonparticipating

If actual mortality, interest, and expenses are better than assumed, a participating (par) policy from a mutual insurer may return the surplus as a policy dividend — legally a non-taxable return of overcharged premium. A nonparticipating (non-par) policy pays no dividends; its guarantees are fixed.

Net vs. Gross Premium and Loading

A life premium has three components. The net premium is built from the mortality cost (expected death claims from the mortality table) discounted by an assumed interest rate the insurer earns on reserves. Adding expense loading (commissions, administration, taxes, profit/contingency) produces the gross premium the policyowner actually pays. On the exam: lower assumed interest raises premium; higher assumed mortality raises premium; loading covers everything that is not pure death cost.

Reserves and the Legal Mortality Tables

The reserve is the insurer's liability — money set aside today to guarantee future claims. As a level-premium whole life policy ages, the overpayment in early years builds the reserve, which combined with future premiums and interest funds the rising mortality cost later. Statutory reserves use the current CSO (Commissioners Standard Ordinary) mortality table. Understanding that level premiums overcharge early and undercharge late explains why permanent policies accumulate cash value.