Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 28155 | Thousand metric tons | NA |
| 2003 | 26639 | Thousand metric tons | -5.38% |
| 2004 | 28763 | Thousand metric tons | 7.97% |
| 2005 | 32458 | Thousand metric tons | 12.85% |
| 2006 | 36200 | Thousand metric tons | 11.53% |
| 2007 | 38400 | Thousand metric tons | 6.08% |
| 2008 | 39844 | Thousand metric tons | 3.76% |
| 2009 | 46900 | Thousand metric tons | 17.71% |
| 2010 | 47800 | Thousand metric tons | 1.92% |
| 2011 | 43384 | Thousand metric tons | -9.24% |
| 2012 | 55200 | Thousand metric tons | 27.24% |
