Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1050 | Thousand metric tons | NA |
| 2004 | 1167 | Thousand metric tons | 11.14% |
| 2005 | 1189 | Thousand metric tons | 1.89% |
| 2006 | 1177 | Thousand metric tons | -1.01% |
| 2007 | 1192 | Thousand metric tons | 1.27% |
| 2008 | 1190 | Thousand metric tons | -0.17% |
| 2009 | 890 | Thousand metric tons | -25.21% |
| 2010 | 1010 | Thousand metric tons | 13.48% |
| 2011 | 1061 | Thousand metric tons | 5.05% |
| 2012 | 1116 | Thousand metric tons | 5.18% |
| 2013 | 1052 | Thousand metric tons | -5.73% |
