Indian industrialist

How do we know who are the richest people in the world? A handful of wealth is in their hands. There is constant competition between them. Sometimes one goes to the top of the list, sometimes another. Elon Musk now tops forbes list of rich people. He has bought one company after the other. But how accurate is the business man's approach on the basis of money alone? Ratan Tata's name is known to the whole world. But why doesn't his name figure in the list of richest people?