回复@张浩_: 巴菲特最大比例的持股是partnership时期的$美国运通(AXP)$ ，为了买美国运通巴菲特直接修改了他在设立partnership时的ground rule：
We diversify substantially less than most investment operations.We might invest up to 40% of our net worth in a single security under conditions coupling an extremely high probability that our facts and reasoning are correct with a very low probability that anything could drastically change the underlying va