Utilize the input text as a context reference, choose the right relationship between Berkshire Hathaway and Warren Buffett from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Legendary US investor Warren Buffett -- in a 2011 letter to shareholders of his Berkshire Hathaway investment group -- famously compared the entire world's gold stock of 170,000 metric tons, valued at $9.6 trillion (pile A) with another set of assets costing an equal amount (pile B).

Answer: director_/_manager