 It is the only country to meet all five UNDP criteria established to measure environmental sustainability.It was ranked 42nd in the world, and third in the Americas, in the 2016 Environmental Performance Index, and was twice ranked the best performing country in the New Economics Foundation's (NEF) Happy Planet Index, which measures environmental sustainability, and was identified by the NEF as the greenest country in the world in 2009.Costa Rica plans to become a carbon-neutral country by 2021.