The interviewer mentions that Warren Buffett has previously invested a significant portion of his net worth in certain ideas, such as American Express and the Washington Post in the 70s.
Buffett confirms that there have been numerous occasions over his 50-year investing career when he would have put at least 75% of his net worth into an idea.
He clarifies that outside of Berkshire Hathaway, his net worth has never been a substantial amount.
Buffett mentions that there have been times when he had more than 100% of his net worth invested in things, possibly due to borrowing or leverage.
He emphasizes that there are rare opportunities that are so compelling that it would be a mistake not to invest a significant portion of one's net worth in them, even up to 75%.
Buffett acknowledges that there have been cases where investors have put an excessively high percentage of their net worth into an idea, citing the example of Long-Term Capital Management (ltcm).
He highlights the importance of proper risk management and cautions against overleveraging or taking excessively large positions.
Buffett mentions specific instances where he would have been confident enough to put a large portion of his net worth into investments, such as cap cities with Tom Murphy in 1974 and Coca-Cola.
He states that diversification is often considered important for inexperienced or "know-nothing" investors but argues that true professionals should focus on finding safe and wise opportunities to concentrate their investments.
Buffett suggests that there are occasions where allocating only 20% of one's net worth to an opportunity would be a wasted opportunity of a lifetime.
He mentions that while working with smaller sums of money, he had more flexibility to load up on investments, but with Berkshire's large capital, such opportunities are rare.