Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 402 | Thousand metric tons | NA |
| 2003 | 424 | Thousand metric tons | 5.47% |
| 2004 | 467.065002441406 | Thousand metric tons | 10.16% |
| 2005 | 552.495971679688 | Thousand metric tons | 18.29% |
| 2006 | 649.943969726563 | Thousand metric tons | 17.64% |
| 2007 | 620 | Thousand metric tons | -4.61% |
| 2008 | 640 | Thousand metric tons | 3.23% |
| 2009 | 800 | Thousand metric tons | 25.00% |
| 2010 | 854 | Thousand metric tons | 6.75% |
| 2011 | 885 | Thousand metric tons | 3.63% |
| 2012 | 1260 | Thousand metric tons | 42.37% |
| 2013 | 1204 | Thousand metric tons | -4.44% |
