| Year | Males: females | Average age (months) |
| 2002 | 1:0 | 16 |
| 2003 | 1:1 | 10 |
| 2004 | 0.5:1 | 9.75 |
| 2005 | 2:1 | 5.9 |
| 2006 | 2.5:1 | 14.4 |
| 2007 | 1.5:1 | 9 |
| 2008 | 3.5:1 | 17.8 |
| 2009 | 2.6:1 | 15.2 |
| 2010 | 3:1 | 10.3 |
| 2011 | 0.7:1 | 14.4 |
| 2012 | 0.8:1 | 17.2 |