The line demarcating the Eastern and Western Hemispheres is an arbitrary convention, unlike the Equator (an imaginary line encircling Earth, equidistant from its poles), which divides the Northern and Southern Hemispheres. The prime meridian at 0° longitude and the antimeridian, at 180° longitude, are the conventionally accepted boundaries, since they divide eastern longitudes from western longitudes. This convention was established (predominantly by Europeans and Americans) in 1884 at the International Meridian Conference held in Washington, D.C. where the standard time concepts of Canadian railroad engineer Sir Sandford Fleming were adopted. Using this demarcation puts portions of Western Europe, West Africa, Oceania, and extreme northeastern Russia in the Western Hemisphere, thereby diluting its usefulness as a geopolitical construct, since all of Eurasia and Africa are typically included in the Eastern Hemisphere. Consequently, the meridians of 20°W and the diametrically opposed 160°E are often used, which includes all of the European and African mainlands, but also includes a small portion of northeast Greenland (typically reckoned as part of North America) and excludes more of eastern Russia and Oceania (e.g., New Zealand). Prior to the global adoption of standard time, numerous prime meridians were decreed by various countries where time was defined by local noon (thereby, local meridian).
The land mass of the Eastern Hemisphere is larger than that of the Western Hemisphere and has a wide variety of habitats.
82% of humans live in the Eastern Hemisphere, and 18% in the Western Hemisphere.