In 2001, it exceeded 10 million tons.

In 2003, it exceeded 20 million tons.

In 2005, it exceeded 30 million tons.

In 2006, it exceeded 40 million tons.

In 2007, it reached 47.5 million tons.

In 2009, it exceeded 10 million tons.

In 2013, it exceeded 200 million tons (200 million tons).