ABSTRACT
Throughout the majority of human history, population growth was very modest with world population not reaching 1 billion until around 1800 A.D. and 2 billion 125 years later [1]. However, from this point, population growth accelerated rapidly until the mid-1960s peaking at just over 2% per year, before decreasing to 1.1% per year in 2010 [2]. World population increased sevenfold between 1800 and 2011, and this period of substantially faster population growth coincided with global economic expansion. In 2011, an expected ~135 million births and 57 million deaths would equate with a net increase in the world population of 78 million people [1].
