From Warren Buffett’s 50th annual shareholder letter for Berkshire Hathaway:

At bottom, a sound insurance operation needs to adhere to four disciplines. It must (1) understand all exposures that might cause a policy to incur losses; (2) conservatively assess the likelihood of any exposure actually causing a loss and the probable cost if it does; (3) set a premium that, on average, will deliver a profit after both prospective loss costs and operating expenses are covered; and (4) be willing to walk away if the appropriate premium can’t be obtained.

Many insurers pass the first three tests and flunk the fourth. They simply can’t turn their back on business that is being eagerly written by their competitors. That old line, “The other guy is doing it, so we must as well,” spells trouble in any business, but in none more so than insurance.