Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3050 | Thousand metric tons | NA |
| 2003 | 2907 | Thousand metric tons | -4.69 % |
| 2004 | 2653.63891601563 | Thousand metric tons | -8.72 % |
| 2005 | 2778.7080078125 | Thousand metric tons | 4.71 % |
| 2006 | 3776.79809570313 | Thousand metric tons | 35.92 % |
| 2007 | 4100 | Thousand metric tons | 8.56 % |
| 2008 | 4207 | Thousand metric tons | 2.61 % |
| 2009 | 3852 | Thousand metric tons | -8.44 % |
| 2010 | 4106 | Thousand metric tons | 6.59 % |
| 2011 | 3997 | Thousand metric tons | -2.65 % |
| 2012 | 4130 | Thousand metric tons | 3.33 % |
