" Consider this. It took the earth’s population thousands of years—from the early dawn of man all the way to the early 1800s—to reach one billion people. Then, astoundingly, it took only about a hundred years to double the population to two billion in the 1920s. After that, it took a mere fifty years for the population to double again to four billion in the 1970s. As you can imagine, we’re well on track to reach eight billion very soon. Just today, the human race added another quarter-million people to planet Earth. A quarter million. And this happens every day—rain or shine. Currently, every year, we’re adding the equivalent of the entire country of Germany. "
― Dan Brown , Inferno (Robert Langdon, #4)