Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 42417 | Thousand metric tons | NA |
| 2003 | 44747 | Thousand metric tons | 5.49% |
| 2004 | 45593 | Thousand metric tons | 1.89% |
| 2005 | 50347 | Thousand metric tons | 10.43% |
| 2006 | 54032.76953125 | Thousand metric tons | 7.32% |
| 2007 | 54720.4453125 | Thousand metric tons | 1.27% |
| 2008 | 42088 | Thousand metric tons | -23.09% |
| 2009 | 29505 | Thousand metric tons | -29.90% |
| 2010 | 26217 | Thousand metric tons | -11.14% |
| 2011 | 22178 | Thousand metric tons | -15.41% |
| 2012 | 15939 | Thousand metric tons | -28.13% |
