Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1028.27294921875 | Thousand metric tons | NA |
| 2004 | 1030.23400878906 | Thousand metric tons | 0.19% |
| 2005 | 1024.0400390625 | Thousand metric tons | -0.60% |
| 2006 | 807.278015136719 | Thousand metric tons | -21.17% |
| 2007 | 741.684997558594 | Thousand metric tons | -8.13% |
| 2008 | 1133.96301269531 | Thousand metric tons | 52.89% |
| 2009 | 1037.88098144531 | Thousand metric tons | -8.47% |
| 2010 | 1082.55895996094 | Thousand metric tons | 4.30% |
| 2011 | 1142.85998535156 | Thousand metric tons | 5.57% |
| 2012 | 958.18701171875 | Thousand metric tons | -16.16% |
| 2013 | 950 | Thousand metric tons | -0.85% |
