Complex sentence: The American oil magnate John D. Rockefeller became the world's first confirmed U.S. dollar billionaire in 1916; as of 2017, there are over 2,000 U.S. dollar billionaires worldwide, with a combined wealth of over US $7.6 trillion.
Split into simpler sentences: The American oil magnate John D. Rockefeller became the world's first confirmed U.S. dollar billionaire in 1916. As of 2017, there are over 2,000 U.S. dollar billionaires worldwide, with a combined wealth of over US $7.6 trillion.