Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 913 | Thousand metric tons | NA |
| 2003 | 891 | Thousand metric tons | -2.41% |
| 2004 | 1044.94396972656 | Thousand metric tons | 17.28% |
| 2005 | 1025.5400390625 | Thousand metric tons | -1.86% |
| 2006 | 1226.31896972656 | Thousand metric tons | 19.58% |
| 2007 | 1283.35705566406 | Thousand metric tons | 4.65% |
| 2008 | 1406 | Thousand metric tons | 9.56% |
| 2009 | 1074 | Thousand metric tons | -23.61% |
| 2010 | 949 | Thousand metric tons | -11.64% |
| 2011 | 893 | Thousand metric tons | -5.90% |
| 2012 | 846 | Thousand metric tons | -5.26% |
