Margin of Safety

'Never count on making a good sale. Have the purchase price be so attractive that even a mediocre sale gives good results.'

Source: "Buffett: The Making of an American Capitalist" (1995)

'If you understood a business perfectly and the future of the business, you would need very little in the way of a margin of safety.'

Source: 1997 Berkshire Hathaway annual meeting

So, the more vulnerable the business is, assuming you still want to invest in it, the larger margin of safety you'd need. If you're driving a truck across a bridge that says it holds 10,000 pounds and you've got a 9,800 pound vehicle, if the bridge is 6 inches above the crevice it covers, you may feel okay, but if it's over the Grand Canyon, you may feel you want a little larger margin of safety.'

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