Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 38027 | Thousand metric tons | NA |
| 2003 | 34010 | Thousand metric tons | -10.56 % |
| 2004 | 34413.2890625 | Thousand metric tons | 1.19 % |
| 2005 | 36673.46875 | Thousand metric tons | 6.57 % |
| 2006 | 39539.6015625 | Thousand metric tons | 7.82 % |
| 2007 | 46406.359375 | Thousand metric tons | 17.37 % |
| 2008 | 51864.8359375 | Thousand metric tons | 11.76 % |
