Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1653 | Thousand metric tons | NA |
| 2003 | 1694 | Thousand metric tons | 2.48% |
| 2004 | 2391 | Thousand metric tons | 41.15% |
| 2005 | 2623.19995117188 | Thousand metric tons | 9.71% |
| 2006 | 2883.80004882813 | Thousand metric tons | 9.93% |
| 2007 | 3152.30004882813 | Thousand metric tons | 9.31% |
| 2008 | 3084 | Thousand metric tons | -2.17% |
| 2009 | 3320 | Thousand metric tons | 7.65% |
| 2010 | 4066 | Thousand metric tons | 22.47% |
| 2011 | 4677 | Thousand metric tons | 15.03% |
| 2012 | 4689 | Thousand metric tons | 0.26% |
