Year	Number
1989	16.43345
1990	14.4363
1991	12.5248
1992	12.30405
1993	11.61681
1994	11.78448
1995	12.13743
1996	11.86643
1997	12.49147
1999	13.24077
2000	13.31002
2001	14.70442
2002	16.32944
2003	17.31461
2004	17.75295
2005	16.89391
2006	16.92965
2007	20.98017
2008	18.6834
2009	16.94827
2010	17.83025
2012	17.29055
2013	17.69155
2014	18.05963
2015	17.69014
2017	14.94604