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% |
| 2009 | 3760000 | Metric tons, gross weight | -3.59% |
| 2010 | 3800000 | Metric tons, gross weight | 1.06% |
| 2011 | 3850000 | Metric tons, gross weight | 1.32% |
| 2012 | 3900000 | Metric tons, gross weight | 1.30% |
