Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 38027 | Thousand metric tons | NA |
| 2003 | 34010 | Thousand metric tons | -10.56% |
| 2004 | 34413.2890625 | Thousand metric tons | 1.19% |
| 2005 | 36673.46875 | Thousand metric tons | 6.57% |
| 2006 | 39539.6015625 | Thousand metric tons | 7.82% |
| 2007 | 46406.359375 | Thousand metric tons | 17.37% |
| 2008 | 51884 | Thousand metric tons | 11.80% |
| 2009 | 51748 | Thousand metric tons | -0.26% |
| 2010 | 59118 | Thousand metric tons | 14.24% |
| 2011 | 64093 | Thousand metric tons | 8.42% |
| 2012 | 68787 | Thousand metric tons | 7.32% |
