Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4140 | Thousand metric tons | NA |
| 2004 | 4283.14208984375 | Thousand metric tons | 3.46% |
| 2005 | 3581.09008789063 | Thousand metric tons | -16.39% |
| 2006 | 3400 | Thousand metric tons | -5.06% |
| 2007 | 3240 | Thousand metric tons | -4.71% |
| 2008 | 3106 | Thousand metric tons | -4.14% |
| 2009 | 2996 | Thousand metric tons | -3.54% |
| 2010 | 2984 | Thousand metric tons | -0.40% |
| 2011 | 3141.19995117188 | Thousand metric tons | 5.27% |
| 2012 | 2707 | Thousand metric tons | -13.82% |
