Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4101 | Thousand metric tons | NA |
| 2004 | 4244 | Thousand metric tons | 3.49% |
| 2005 | 4098 | Thousand metric tons | -3.44% |
| 2006 | 3945.97509765625 | Thousand metric tons | -3.71% |
| 2007 | 3923.23388671875 | Thousand metric tons | -0.58% |
| 2008 | 2945 | Thousand metric tons | -24.93% |
| 2009 | 1575 | Thousand metric tons | -46.52% |
| 2010 | 1880 | Thousand metric tons | 19.37% |
| 2011 | 1600 | Thousand metric tons | -14.89% |
| 2012 | 1500 | Thousand metric tons | -6.25% |
