Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1202 | Thousand metric tons | NA |
| 2003 | 1378 | Thousand metric tons | 14.64% |
| 2004 | 1554 | Thousand metric tons | 12.77% |
| 2005 | 1579 | Thousand metric tons | 1.61% |
| 2006 | 2339.63696289063 | Thousand metric tons | 48.17% |
| 2007 | 1982.10095214844 | Thousand metric tons | -15.28% |
| 2008 | 2077 | Thousand metric tons | 4.79% |
| 2009 | 1307 | Thousand metric tons | -37.07% |
| 2010 | 1220 | Thousand metric tons | -6.66% |
| 2011 | 1280 | Thousand metric tons | 4.92% |
| 2012 | 1300 | Thousand metric tons | 1.56% |
