Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 4594 | Thousand metric tons | NA |
| 2003 | 5239.80517578125 | Thousand metric tons | 14.06% |
| 2004 | 6439.40087890625 | Thousand metric tons | 22.89% |
| 2005 | 6810.40478515625 | Thousand metric tons | 5.76% |
| 2006 | 7138 | Thousand metric tons | 4.81% |
| 2007 | 7614 | Thousand metric tons | 6.67% |
| 2008 | 7823 | Thousand metric tons | 2.74% |
| 2009 | 6698 | Thousand metric tons | -14.38% |
| 2010 | 9160 | Thousand metric tons | 36.76% |
| 2011 | 10626 | Thousand metric tons | 16.00% |
| 2012 | 10132 | Thousand metric tons | -4.65% |
