Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2698577 | Metric tons, gross weight | NA |
| 2003 | 2210000 | Metric tons, gross weight | -18.10 % |
| 2004 | 2948944 | Metric tons, gross weight | 33.44 % |
| 2005 | 3255162 | Metric tons, gross weight | 10.38 % |
| 2006 | 3600400 | Metric tons, gross weight | 10.61 % |
| 2007 | 3320000 | Metric tons, gross weight | -7.79 % |
| 2008 | 3900000 | Metric tons, gross weight | 17.47 % |
