America is home to 735 billionaires with a collective worth greater than $4.7 trillion, according to Forbes. There were just 424 billionaires in 2012, Forbes found, and only 243 a decade before that. The billionaires keep multiplying.In this article, Willy Staley uses information from the first billionaire count — commissioned in 1981 by the entrepreneur Malcolm Forbes for his own magazine — to consider the reasons behind the rapid increase in American billionaires, but also the changing attitudes on publicizing the details of one’s wealth.Many factors enabled American entrepreneurs to amass such enormous fortunes, including the Reagan administration’s policies, the arrival of computer technology, the creation of a more globalized economy and the rise of the developing world.Yet despite the conspicuous consumption this level of wealth often encourages, Staley finds that few billionaires want to be discovered. So how do you keep tabs on America’s billionaires?This story was written by Willy Staley and recorded by Audm. To hear more audio stories from publications like The New York Times, download Audm for iPhone or Android.