Year	Number
1970	40.89375
1971	40.15599
1972	40.91347
1973	41.98083
1974	42.4966
1975	42.91043
1976	42.9166
1977	42.49788
1978	41.35338
1979	41.13729
1980	43.04729
1981	43.89775
1982	43.63343
1983	42.85045
1984	41.05402
1985	40.35504
1986	39.8395
1987	40.27998
1988	41.56661
1989	41.80222
1990	41.70949
1991	41.98983
1992	41.64935
1993	41.71713
1994	42.65813
1995	42.71009
1996	42.36315
1997	43.55003
1998	43.47907
1999	42.29028
2000	43.20584
2001	43.61402
2002	44.98157
2003	45.34971
2004	44.72152
2005	44.78525
2006	44.12178
2007	43.8347
2008	43.51757
2009	43.08665
2010	41.86114
2011	41.02505
2012	40.1191
2013	39.54362
2014	38.96898
2015	38.00919
2016	37.41777
2017	37.10324
2018	37.15033