It's no surprise that the world's population is at an all-time high - exceeding 7 billion - although many might not know that it increased by 5 billion during the past century alone, rising from less than 2 billion in 1914. And many people would be surprised - even shocked - to know that over the past three decades, fertility rates have plummeted in many parts of the world, including China, Japan and even significant regions of India.