Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 848 | Thousand metric tons | NA |
| 2003 | 1013 | Thousand metric tons | 19.46% |
| 2004 | 1427.5 | Thousand metric tons | 40.92% |
| 2005 | 1537.90002441406 | Thousand metric tons | 7.73% |
| 2006 | 1622 | Thousand metric tons | 5.47% |
| 2007 | 1730.80004882813 | Thousand metric tons | 6.71% |
| 2008 | 1595 | Thousand metric tons | -7.85% |
| 2009 | 1286 | Thousand metric tons | -19.37% |
| 2010 | 1279 | Thousand metric tons | -0.54% |
| 2011 | 1425 | Thousand metric tons | 11.42% |
| 2012 | 1966 | Thousand metric tons | 37.96% |
