Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 419.371002197266 | Thousand metric tons | NA |
| 2003 | 429.170013427734 | Thousand metric tons | 2.34% |
| 2004 | 412.238006591797 | Thousand metric tons | -3.95% |
| 2005 | 362.105987548828 | Thousand metric tons | -12.16% |
| 2006 | 411.972991943359 | Thousand metric tons | 13.77% |
| 2007 | 421.710998535156 | Thousand metric tons | 2.36% |
| 2008 | 455.100006103516 | Thousand metric tons | 7.92% |
| 2009 | 363.699005126953 | Thousand metric tons | -20.08% |
| 2010 | 390.352996826172 | Thousand metric tons | 7.33% |
| 2011 | 489.091003417969 | Thousand metric tons | 25.29% |
| 2012 | 450 | Thousand metric tons | -7.99% |
