Year	Number
1970	37.33407
1971	37.22682
1972	37.15836
1973	37.16761
1974	37.04685
1975	37.19154
1976	37.43987
1977	37.6493
1978	36.46688
1979	36.42011
1980	37.27141
1981	37.34616
1982	37.36096
1983	36.99421
1984	36.89321
1985	36.97431
1986	36.69579
1987	37.09672
1988	36.67943
1989	35.40412
1990	36.18692
1991	36.14944
1992	36.10129
1993	36.62215
1994	37.8027
1995	38.18595
1996	38.1633
1997	40.68197
1998	41.16626
1999	41.08939
2000	42.29402
2001	42.4573
2002	43.14226
2003	42.43759
2004	42.63907
2005	42.77139
2006	43.42119
2007	44.30918
2008	43.82135
2009	43.17603
2010	41.61892
2011	40.82749
2012	42.2331
2013	38.79979
2014	37.98595
2015	37.50958
2016	37.50943
2017	37.37176
2018	37.36509