Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3478.05688476563 | Thousand metric tons | NA |
| 2004 | 3591.7470703125 | Thousand metric tons | 3.27% |
| 2005 | 3647.07202148438 | Thousand metric tons | 1.54% |
| 2006 | 3717.90698242188 | Thousand metric tons | 1.94% |
| 2007 | 3955.4169921875 | Thousand metric tons | 6.39% |
| 2008 | 4190 | Thousand metric tons | 5.93% |
| 2009 | 3815 | Thousand metric tons | -8.95% |
| 2010 | 3947 | Thousand metric tons | 3.46% |
| 2011 | 3992.9990234375 | Thousand metric tons | 1.17% |
| 2012 | 3924 | Thousand metric tons | -1.73% |
| 2013 | 3724 | Thousand metric tons | -5.10% |
