World hydroelectric power generation has risen steadily by an average 3 percent annually over the past four decades. In 2011, at 3,500 billion kilowatt-hours, hydroelectricity accounted for roughly 16 percent of global electricity generation, almost all produced by the world’s 45,000-plus large dams. Today hydropower is generated in over 160 countries. Four countries dominate the hydropower landscape: China, Brazil, Canada, and the United States. Together they produce more than half of the world’s hydroelectricity.