Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2369400 | Metric tons, gross weight | NA |
| 2003 | 2927500 | Metric tons, gross weight | 23.55% |
| 2004 | 3287100 | Metric tons, gross weight | 12.28% |
| 2005 | 3581242 | Metric tons, gross weight | 8.95% |
| 2006 | 3366078 | Metric tons, gross weight | -6.01% |
| 2007 | 3687200 | Metric tons, gross weight | 9.54% |
| 2008 | 3552000 | Metric tons, gross weight | -3.67% |
| 2009 | 3544000 | Metric tons, gross weight | -0.23% |
| 2010 | 3760000 | Metric tons, gross weight | 6.09% |
| 2011 | 3800000 | Metric tons, gross weight | 1.06% |
| 2012 | 4000000 | Metric tons, gross weight | 5.26% |
