Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 101 | Thousand metric tons | NA |
| 2003 | 110 | Thousand metric tons | 8.91% |
| 2004 | 104.28800201416 | Thousand metric tons | -5.19% |
| 2005 | 101.127998352051 | Thousand metric tons | -3.03% |
| 2006 | 102.588996887207 | Thousand metric tons | 1.44% |
| 2007 | 103.033996582031 | Thousand metric tons | 0.43% |
| 2008 | 103 | Thousand metric tons | -0.03% |
| 2009 | 92 | Thousand metric tons | -10.68% |
| 2010 | 95 | Thousand metric tons | 3.26% |
| 2011 | 94 | Thousand metric tons | -1.05% |
| 2012 | 100 | Thousand metric tons | 6.38% |
