Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1018 | Thousand metric tons | NA |
| 2003 | 1164 | Thousand metric tons | 14.34% |
| 2004 | 1400 | Thousand metric tons | 20.27% |
| 2005 | 1500 | Thousand metric tons | 7.14% |
| 2006 | 1600 | Thousand metric tons | 6.67% |
| 2007 | 1700 | Thousand metric tons | 6.25% |
| 2008 | 1800 | Thousand metric tons | 5.88% |
| 2009 | 1900 | Thousand metric tons | 5.56% |
| 2010 | 2600 | Thousand metric tons | 36.84% |
| 2011 | 2200 | Thousand metric tons | -15.38% |
| 2012 | 2400 | Thousand metric tons | 9.09% |
