Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3378 | Thousand metric tons | NA |
| 2003 | 3654 | Thousand metric tons | 8.17% |
| 2004 | 3811 | Thousand metric tons | 4.30% |
| 2005 | 3480.94897460938 | Thousand metric tons | -8.66% |
| 2006 | 3597.96508789063 | Thousand metric tons | 3.36% |
| 2007 | 3524.39111328125 | Thousand metric tons | -2.04% |
| 2008 | 3403 | Thousand metric tons | -3.44% |
| 2009 | 2655 | Thousand metric tons | -21.98% |
| 2010 | 2488 | Thousand metric tons | -6.29% |
| 2011 | 2467 | Thousand metric tons | -0.84% |
| 2012 | 2500 | Thousand metric tons | 1.34% |
