Warren Buffett's Berkshire Hathaway has been welcomed into the benchmark S&P 500 index with a surge of trading just before today's close at the New York Stock Exchange.
CNBC's Maria Bartiromo reports there was an enormous crowd around the Berkshire post on the floor of the NYSE.
Index mutual funds that mimic the performance of the S&P had to buy Berkshire Class B shares because the stock is being added to the index after today's close.
Today's Wall Street Journal notes that over $1 trillion of investors' money "directly tracks" the S&P.
Berkshire B shares fell to a low of $74.57 around 1p ET today, and then rebounded to end the day at $76.90, a gain of $0.21, or 0.27 percent. That's 13.1 percent above the $68 close on January 26, the day S&P announced Buffett would join the S&P.