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. 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.
We believe that according the name 'investors' to institutions that trade actively is like calling someone who repeatedly engages in one-night stands a 'romantic.'
Many stock options in the corporate world have worked in exactly that fashion: they have gained in value simply because management retained earnings, not because it did well with the capital in its hands.
For some reason, people take their cues from price action rather than from values. What doesn't work is when you start doing things that you don't understand or because they worked last week for somebody else. The dumbest reason in the world to buy a stock is because it's going up.
In our view, though, investment students need only two well-taught courses-How to Value a Business, and How to Think about Market Prices. Your goal as an investor should simply be to purchase, at a rational price, a part interest in an easily-understandable business who's earnings are virtually certain to be materially higher five, ten and twenty years from now.
If I knew where I was going to want to live the next five or 10 years I would buy a home and I'd finance it with a 30-year mortgage... It's a terrific deal.
So some guy may know how to make money in cocoa beans, but I don't so I just let him have that. But it's got to be something I understand. It's got to be a business with fundamentally good economics. It's got to be a management that I like and trust and admire. And it's got to be a price that makes sense.