Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 210.815002441406 | Thousand metric tons | NA |
| 2004 | 196.330001831055 | Thousand metric tons | -6.87% |
| 2005 | 196.253997802734 | Thousand metric tons | -0.04% |
| 2006 | 204.190002441406 | Thousand metric tons | 4.04% |
| 2007 | 220 | Thousand metric tons | 7.74% |
| 2008 | 147.328002929688 | Thousand metric tons | -33.03% |
| 2009 | 163.205993652344 | Thousand metric tons | 10.78% |
| 2010 | 197.699005126953 | Thousand metric tons | 21.13% |
| 2011 | 232.908996582031 | Thousand metric tons | 17.81% |
| 2012 | 180 | Thousand metric tons | -22.72% |
| 2013 | 200 | Thousand metric tons | 11.11% |
