Some people become richer or poorer within days of publication. We list  individuals rather than multigenerational families who share fortunes,  though we include wealth belonging to a billionaire’s spouse and  children if that person is the founder of the fortune. In some cases we  list siblings or couples together if the ownership breakdown among them  isn’t clear, but here an estimated net worth of $1 billion per person is  needed to make the cut. We value a variety of assets, including private  companies, real estate, art and more. We don’t pretend to know each  billionaire’s private balance sheet (though some provide it). When  documentation isn’t supplied or available, we discount fortunes. For  daily updates of net worths, go to www.forbes.com/real-time-billionaires.