Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 55514 | Thousand metric tons | NA |
| 2003 | 59194 | Thousand metric tons | 6.63% |
| 2004 | 56955 | Thousand metric tons | -3.78% |
| 2005 | 51391 | Thousand metric tons | -9.77% |
| 2006 | 53971 | Thousand metric tons | 5.02% |
| 2007 | 57042 | Thousand metric tons | 5.69% |
| 2008 | 51653 | Thousand metric tons | -9.45% |
| 2009 | 50126 | Thousand metric tons | -2.96% |
| 2010 | 47420 | Thousand metric tons | -5.40% |
| 2011 | 48249 | Thousand metric tons | 1.75% |
| 2012 | 47087 | Thousand metric tons | -2.41% |
