Additions and subtractions to the S&P 500 are normally a ho-hum affair. The 509th biggest company in the U.S. might jump to 497th place, and thus into the index. Investors who track it buy the one stock and sell another.
But no one has ever tried to add Tesla Inc., a $555 billion company prone to huge swings in price. That’s happening next month, and it’s causing headaches across Wall Street.
To…
