Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3141 | Thousand metric tons | NA |
| 2003 | 3147 | Thousand metric tons | 0.19% |
| 2004 | 3158.30810546875 | Thousand metric tons | 0.36% |
| 2005 | 3498.68505859375 | Thousand metric tons | 10.78% |
| 2006 | 3592.50903320313 | Thousand metric tons | 2.68% |
| 2007 | 3718 | Thousand metric tons | 3.49% |
| 2008 | 4157 | Thousand metric tons | 11.81% |
| 2009 | 3011 | Thousand metric tons | -27.57% |
| 2010 | 2888 | Thousand metric tons | -4.09% |
| 2011 | 3219 | Thousand metric tons | 11.46% |
| 2012 | 2915 | Thousand metric tons | -9.44% |
