Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 450 | Thousand metric tons | NA |
| 2003 | 450 | Thousand metric tons | 0.00% |
| 2004 | 550 | Thousand metric tons | 22.22% |
| 2005 | 650 | Thousand metric tons | 18.18% |
| 2006 | 800 | Thousand metric tons | 23.08% |
| 2007 | 900 | Thousand metric tons | 12.50% |
| 2008 | 1025 | Thousand metric tons | 13.89% |
| 2009 | 1100 | Thousand metric tons | 7.32% |
| 2010 | 1140 | Thousand metric tons | 3.64% |
| 2011 | 1500 | Thousand metric tons | 31.58% |
| 2012 | 1900 | Thousand metric tons | 26.67% |
