the worlds richest men, including Elon Musk and Jeff Bezos, have much of their wealth in the form of stock. As their stock rises in value, they are able to finance lavish lifestyles by taking out loans secured by their stock holdings. But loans are not taxed as income, and in many cases the interest payments are tax deductible. The rising value of stock holdings -- known as unrealized gains -- is also not taxed as income. Capital gains taxes are only imposed when the stock is sold. s a result, some 400 billionaire families paid an average federal tax...