Year	Number
1998	22.9542
1999	21.32567
2000	20.21488
2001	19.14833
2002	18.99961
2003	24.62398
2004	22.38328
2006	23.86738
2007	22.90224
2008	18.72004
2011	26.46551
2012	19.2926