Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 900 | Thousand metric tons | NA |
| 2003 | 1130 | Thousand metric tons | 25.56% |
| 2004 | 1315.93395996094 | Thousand metric tons | 16.45% |
| 2005 | 1568.6240234375 | Thousand metric tons | 19.20% |
| 2006 | 1676 | Thousand metric tons | 6.85% |
| 2007 | 1800 | Thousand metric tons | 7.40% |
| 2008 | 1834 | Thousand metric tons | 1.89% |
| 2009 | 2100 | Thousand metric tons | 14.50% |
| 2010 | 2900 | Thousand metric tons | 38.10% |
| 2011 | 3300 | Thousand metric tons | 13.79% |
| 2012 | 3000 | Thousand metric tons | -9.09% |
