Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 144 | Thousand metric tons | NA |
| 2003 | 169 | Thousand metric tons | 17.36% |
| 2004 | 180.460006713867 | Thousand metric tons | 6.78% |
| 2005 | 172.119995117188 | Thousand metric tons | -4.62% |
| 2006 | 234.440002441406 | Thousand metric tons | 36.21% |
| 2007 | 235.830001831055 | Thousand metric tons | 0.59% |
| 2008 | 254 | Thousand metric tons | 7.70% |
| 2009 | 236 | Thousand metric tons | -7.09% |
| 2010 | 301 | Thousand metric tons | 27.54% |
| 2011 | 311 | Thousand metric tons | 3.32% |
| 2012 | 335 | Thousand metric tons | 7.72% |
