Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5450 | Thousand metric tons | NA |
| 2004 | 6670 | Thousand metric tons | 22.39% |
| 2005 | 7800 | Thousand metric tons | 16.94% |
| 2006 | 9360 | Thousand metric tons | 20.00% |
| 2007 | 12600 | Thousand metric tons | 34.62% |
| 2008 | 13200 | Thousand metric tons | 4.76% |
| 2009 | 12900 | Thousand metric tons | -2.27% |
| 2010 | 16200 | Thousand metric tons | 25.58% |
| 2011 | 18100 | Thousand metric tons | 11.73% |
| 2012 | 20300 | Thousand metric tons | 12.15% |
| 2013 | 22100 | Thousand metric tons | 8.87% |
