It takes 9 zeros to express a billion of anything in our numerical system.  According to the Census Bureau, as of tomorrow (July 11^th) the world population will reach 7.58 billion.  The Bureau predicts however, the population growth rate will begin declining (1%) starting 2020-2021.  Between 1920 and 1980, the population more than doubled from 2 billion to almost 4.5 billion. The Bureau’s projections and an article on how it keeps track of world population can be viewed HERE.