In "The Population Bomb"s opening lines the authors state that nothing can prevent famines in which hundreds of millions of people will die during the 1970s (amended to 1970s and 1980s in later editions), and that there would be "a substantial increase in the world death rate." Although many lives could be saved through dramatic action, it was already too late to prevent a substantial increase in the global death rate. However, in reality the global death rate has continued to decline substantially since then, from 13/1000 in 1965–74 to 10/1000 from 1985–1990. Meanwhile, the population of the world has more than doubled, while calories consumed/person have increased 24%. The UN does not keep official death-by-hunger statistics so it is hard to measure whether the "hundreds of millions of deaths" number is correct. Ehrlich himself suggested in 2009 that between 200-300 million had died of hunger since 1968. However, that is measured over 40 years rather than the ten to twenty foreseen in the book, so it can be seen as significantly fewer than predicted.