Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1857.4990234375 | Thousand metric tons | NA |
| 2004 | 1894 | Thousand metric tons | 1.97% |
| 2005 | 1903 | Thousand metric tons | 0.48% |
| 2006 | 1932 | Thousand metric tons | 1.52% |
| 2007 | 1957 | Thousand metric tons | 1.29% |
| 2008 | 1974 | Thousand metric tons | 0.87% |
| 2009 | 1943 | Thousand metric tons | -1.57% |
| 2010 | 1928 | Thousand metric tons | -0.77% |
| 2011 | 1945 | Thousand metric tons | 0.88% |
| 2012 | 1864 | Thousand metric tons | -4.16% |
| 2013 | 1778 | Thousand metric tons | -4.61% |
