Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 915.768981933594 | Thousand metric tons | NA |
| 2004 | 1085.41198730469 | Thousand metric tons | 18.52% |
| 2005 | 1151.44299316406 | Thousand metric tons | 6.08% |
| 2006 | 1081.35205078125 | Thousand metric tons | -6.09% |
| 2007 | 1233.53503417969 | Thousand metric tons | 14.07% |
| 2008 | 1400.76599121094 | Thousand metric tons | 13.56% |
| 2009 | 1404.52099609375 | Thousand metric tons | 0.27% |
| 2010 | 1326.29296875 | Thousand metric tons | -5.57% |
| 2011 | 1236.84301757813 | Thousand metric tons | -6.74% |
| 2012 | 1267.47595214844 | Thousand metric tons | 2.48% |
| 2013 | 1358.14794921875 | Thousand metric tons | 7.15% |
