Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3462 | Thousand metric tons | NA |
| 2003 | 3622 | Thousand metric tons | 4.62% |
| 2004 | 3797.60302734375 | Thousand metric tons | 4.85% |
| 2005 | 3999.1220703125 | Thousand metric tons | 5.31% |
| 2006 | 4111.533203125 | Thousand metric tons | 2.81% |
| 2007 | 4439.966796875 | Thousand metric tons | 7.99% |
| 2008 | 4622 | Thousand metric tons | 4.10% |
| 2009 | 3876 | Thousand metric tons | -16.14% |
| 2010 | 3871 | Thousand metric tons | -0.13% |
| 2011 | 4406 | Thousand metric tons | 13.82% |
| 2012 | 4722 | Thousand metric tons | 7.17% |
