Berkshire Hathaway Letters to Shareholders: 1965-2024

by Warren Buffett

Our main business — though we have others of great importance — is insurance. To understand Berkshire, therefore, it is necessary that you understand how to evaluate an insurance company. The key determinants are: (1) the amount of float that the business generates; (2) its cost; and (3) most critical of all, the long-term outlook for both of these factors. To begin with, float is money we hold but don't own. In an insurance operation, float arises because premiums are received before losses are paid, an interval that sometimes extends over many years. During that time, the insurer invests the money. This pleasant activity typically carries with it a downside: The premiums that an insurer takes in usually do not cover the losses and expenses it eventually must pay. That leaves it running an "underwriting loss," which is the cost of float. An insurance business has value if its cost of float over time is less than the cost the company would otherwise incur to obtain funds. But the business is a lemon if its cost of float is higher than market rates for money.