Each year, Forbes employs a team of more than 50 reporters from a variety of countries to track the activity of the world's wealthiest individuals.
According to Forbes, they received three types of responses – some people try to inflate their wealth, others cooperate but leave out details, and some refuse to answer any questions.
Business deals are then scrutinized and estimates of valuable assets – land, homes, vehicles, artwork, etc.
Since stock prices fluctuate rapidly, an individual's true wealth and ranking at the time of publication may vary from their situation when the list was compiled.
[1] Family fortunes dispersed over a large number of relatives are included only if those individuals' holdings are worth more than a billion dollars.