Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1200 | Thousand metric tons | NA |
| 2003 | 1210 | Thousand metric tons | 0.83% |
| 2004 | 2487.9951171875 | Thousand metric tons | 105.62% |
| 2005 | 2905.23388671875 | Thousand metric tons | 16.77% |
| 2006 | 2859.96899414063 | Thousand metric tons | -1.56% |
| 2007 | 5458.7568359375 | Thousand metric tons | 90.87% |
| 2008 | 5400 | Thousand metric tons | -1.08% |
| 2009 | 5101 | Thousand metric tons | -5.54% |
| 2010 | 4441 | Thousand metric tons | -12.94% |
| 2011 | 5939 | Thousand metric tons | 33.73% |
| 2012 | 2563 | Thousand metric tons | -56.84% |
| 2013 | 4100 | Thousand metric tons | 59.97% |
