Year	Number
1970	24.20997
1971	24.79898
1972	24.63081
1973	24.40618
1974	24.89183
1975	23.90654
1976	22.87356
1978	23.70726
1979	24.63704
1993	18.01642
1994	16.85544
1995	16.92637
1996	17.13345
1997	15.3981
1998	14.84451
1999	14.56158
2000	14.65643
2001	13.73876
2002	13.886
2003	14.04
2004	13.51442
2005	13.71684
2006	12.92197
2007	12.46695
2008	13.05075
2009	13.82051
2010	12.54703
2011	13.25457
2012	12.55556
2013	13.13464
2014	13.31118
2015	13.72171
2016	13.98602
2017	14.03261
2018	14.48826