Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3558 | Thousand metric tons | NA |
| 2003 | 3515 | Thousand metric tons | -1.21% |
| 2004 | 3907.60009765625 | Thousand metric tons | 11.17% |
| 2005 | 4045.89990234375 | Thousand metric tons | 3.54% |
| 2006 | 3967.39990234375 | Thousand metric tons | -1.94% |
| 2007 | 4051 | Thousand metric tons | 2.11% |
| 2008 | 4375 | Thousand metric tons | 8.00% |
| 2009 | 3876 | Thousand metric tons | -11.41% |
| 2010 | 3929 | Thousand metric tons | 1.37% |
| 2011 | 4000 | Thousand metric tons | 1.81% |
| 2012 | 4900 | Thousand metric tons | 22.50% |
