Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 100 | Thousand metric tons | NA |
| 2003 | 100 | Thousand metric tons | 0.00% |
| 2004 | 114.762001037598 | Thousand metric tons | 14.76% |
| 2005 | 119.302001953125 | Thousand metric tons | 3.96% |
| 2006 | 133.074005126953 | Thousand metric tons | 11.54% |
| 2007 | 134 | Thousand metric tons | 0.70% |
| 2008 | 137 | Thousand metric tons | 2.24% |
| 2009 | 138 | Thousand metric tons | 0.73% |
| 2010 | 160 | Thousand metric tons | 15.94% |
| 2011 | 145 | Thousand metric tons | -9.38% |
| 2012 | 124 | Thousand metric tons | -14.48% |
