Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.7% of the Earth's total surface area and comprises 30% of its land area. With approximately 4.3 billion people, it hosts 60% of the world's current human population. Asia has a high growth rate in the modern era. For instance, during the 20th century, Asia's population nearly quadrupled. Asia is defined as comprising the eastwards four-fifths of Eurasia.