And that is only a part of the story...:) The cash flow at companies that Berkshire owns large stakes in (Coke, American Express, IBM, Wells Fargo, etc, etc, etc) continues to improve those companies. GAAP accounting rules only allow Berkshire to report the earnings that are paid to it as dividends... however, all the money retained by those companies that are attributed to Berkshire continue to make Berkshire richer and richer.
As an example, Coke and IBM use a lot of their retained earnings to buy back shares... which increases the share of ownership that Berkshire has in those companies... all without it being reported as 'earnings' to Berkshire (which is why Berkshire's earnings reports actually understate how much wealth is being amassed). Berkshire owned 8.8% of Coke with the 400 million shares.. now that same 400 million shares gives Berkshire 8.9% ownership of Coke. That means that ever more of Coke's earnings are attributable to Berkshire's ownership...:)
That is the value of compounding.. and why Berkshire continues to have an ever growing empire... it is also why if you own even one share of Berkshire, your wealth goes up... even if you don't buy another one.