Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6604 | Thousand metric tons | NA |
| 2003 | 7337 | Thousand metric tons | 11.10% |
| 2004 | 7822.38623046875 | Thousand metric tons | 6.62% |
| 2005 | 9959.22265625 | Thousand metric tons | 27.32% |
| 2006 | 10038.130859375 | Thousand metric tons | 0.79% |
| 2007 | 11067.759765625 | Thousand metric tons | 10.26% |
| 2008 | 10456 | Thousand metric tons | -5.53% |
| 2009 | 9232 | Thousand metric tons | -11.71% |
| 2010 | 9488 | Thousand metric tons | 2.77% |
| 2011 | 10777 | Thousand metric tons | 13.59% |
| 2012 | 10925 | Thousand metric tons | 1.37% |
