Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 7268.80322265625 | Thousand metric tons | NA |
| 2003 | 8011.02294921875 | Thousand metric tons | 10.21 % |
| 2004 | 8003.4912109375 | Thousand metric tons | -0.09 % |
| 2005 | 7862.06103515625 | Thousand metric tons | -1.77 % |
| 2006 | 8628.2001953125 | Thousand metric tons | 9.74 % |
| 2007 | 8817.7001953125 | Thousand metric tons | 2.20 % |
| 2008 | 9315.580078125 | Thousand metric tons | 5.65 % |
| 2009 | 8242.2998046875 | Thousand metric tons | -11.52 % |
| 2010 | 9129.5 | Thousand metric tons | 10.76 % |
| 2011 | 12624.599609375 | Thousand metric tons | 38.28 % |
| 2012 | 17330.099609375 | Thousand metric tons | 37.27 % |
