Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1438 | Thousand metric tons | NA |
| 2003 | 1637 | Thousand metric tons | 13.84 % |
| 2004 | 1688.9169921875 | Thousand metric tons | 3.17 % |
| 2005 | 1804.64501953125 | Thousand metric tons | 6.85 % |
| 2006 | 1786.48803710938 | Thousand metric tons | -1.01 % |
| 2007 | 1872.53100585938 | Thousand metric tons | 4.82 % |
| 2008 | 1914 | Thousand metric tons | 2.21 % |
| 2009 | 1484 | Thousand metric tons | -22.47 % |
| 2010 | 1329 | Thousand metric tons | -10.44 % |
| 2011 | 1207 | Thousand metric tons | -9.18 % |
| 2012 | 1300 | Thousand metric tons | 7.71 % |
