What Elon Musk’s trillion means in real terms

NEW YORK—Catapulted by the market debut of his rocket company SpaceX, Elon Musk is now the world’s first trillionaire. That level of wealth, all owned by just one person, was once unfathomable. Before Friday, the trillion-dollar mark was reserved for measures like the gross domestic product (GDP) or staggering debt of a handful of major