Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3918 | Thousand metric tons | NA |
| 2003 | 3886 | Thousand metric tons | -0.82% |
| 2004 | 4355.7001953125 | Thousand metric tons | 12.09% |
| 2005 | 4559.7001953125 | Thousand metric tons | 4.68% |
| 2006 | 4852.2001953125 | Thousand metric tons | 6.41% |
| 2007 | 5202.5 | Thousand metric tons | 7.22% |
| 2008 | 5309 | Thousand metric tons | 2.05% |
| 2009 | 4646 | Thousand metric tons | -12.49% |
| 2010 | 4254 | Thousand metric tons | -8.44% |
| 2011 | 4427 | Thousand metric tons | 4.07% |
| 2012 | 4455 | Thousand metric tons | 0.63% |
