When he buys a stock, Warren Buffett places more emphasis on one factor above almost any other.
Since 1986 he has mentioned this single trait 20 times in his annual shareholder letters. He calls it "essential for sustained success."
However, you won't find it listed on a company's balance sheet. Its value doesn't rise and fall with the market. And even if a company reports great earnings, the worth of this one advantage still can't be calculated.
But that doesn't keep it from being a company's most valuable possession.
Take the nasty bear market of 2008 and 2009. From its peak...