Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1198 | Thousand metric tons | NA |
| 2003 | 1493 | Thousand metric tons | 24.62% |
| 2004 | 1295 | Thousand metric tons | -13.26% |
| 2005 | 1357 | Thousand metric tons | 4.79% |
| 2006 | 1684.50695800781 | Thousand metric tons | 24.13% |
| 2007 | 1742.53405761719 | Thousand metric tons | 3.44% |
| 2008 | 1633 | Thousand metric tons | -6.29% |
| 2009 | 1052 | Thousand metric tons | -35.58% |
| 2010 | 1200 | Thousand metric tons | 14.07% |
| 2011 | 1514 | Thousand metric tons | 26.17% |
| 2012 | 1500 | Thousand metric tons | -0.92% |
