Coal is widely considered one of the most affordable sources of energy in the world. World coal reserves are abundant. These also have a wide distribution pattern, with particular concentration in countries including the United States, Russia, China, Australia, and India. The continuous rise in global coal-fired generation in recent years has resulted from various macro factors including global economic growth; price increases of other energies, such as oil and natural gas; and improvements in coal mining processing technologies; and productivity. Coal will continue to hold an increasing share in the energy mix of emerging countries, therefore, growth in coal demand is unlikely to stagnate.