Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3980 | Thousand metric tons | NA |
| 2003 | 4000 | Thousand metric tons | 0.50% |
| 2004 | 4604.201171875 | Thousand metric tons | 15.11% |
| 2005 | 5107.2578125 | Thousand metric tons | 10.93% |
| 2006 | 5782.4189453125 | Thousand metric tons | 13.22% |
| 2007 | 6231.02294921875 | Thousand metric tons | 7.76% |
| 2008 | 6922 | Thousand metric tons | 11.09% |
| 2009 | 6862 | Thousand metric tons | -0.87% |
| 2010 | 8396 | Thousand metric tons | 22.36% |
| 2011 | 8500 | Thousand metric tons | 1.24% |
| 2012 | 9000 | Thousand metric tons | 5.88% |
