Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1192.40002441406 | Thousand metric tons | NA |
| 2004 | 1321.69995117188 | Thousand metric tons | 10.84% |
| 2005 | 1372.40002441406 | Thousand metric tons | 3.84% |
| 2006 | 1330.80004882813 | Thousand metric tons | -3.03% |
| 2007 | 1357 | Thousand metric tons | 1.97% |
| 2008 | 1358 | Thousand metric tons | 0.07% |
| 2009 | 1139 | Thousand metric tons | -16.13% |
| 2010 | 1109 | Thousand metric tons | -2.63% |
| 2011 | 1122 | Thousand metric tons | 1.17% |
| 2012 | 1145 | Thousand metric tons | 2.05% |
| 2013 | 1100 | Thousand metric tons | -3.93% |
