Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 26550 | Thousand metric tons | NA |
| 2004 | 25117 | Thousand metric tons | -5.40% |
| 2005 | 27125 | Thousand metric tons | 7.99% |
| 2006 | 28300 | Thousand metric tons | 4.33% |
| 2007 | 28800 | Thousand metric tons | 1.77% |
| 2008 | 29000 | Thousand metric tons | 0.69% |
| 2009 | 34000 | Thousand metric tons | 17.24% |
| 2010 | 38685 | Thousand metric tons | 13.78% |
| 2011 | 43600 | Thousand metric tons | 12.71% |
| 2012 | 48000 | Thousand metric tons | 10.09% |
