Year	Number
1970	37.99029
1971	37.47175
1972	37.73208
1973	38.68888
1974	38.98468
1975	39.10673
1976	39.16872
1977	39.0177
1978	37.52007
1979	37.55486
1980	38.82283
1981	39.12985
1982	39.09711
1983	38.32889
1984	37.85947
1985	37.89948
1986	37.68398
1987	38.12844
1988	38.58418
1989	38.16481
1990	38.65156
1991	38.55658
1992	38.08996
1993	37.85862
1994	38.25746
1995	38.2803
1996	37.57511
1997	38.49205
1998	38.57297
1999	38.6285
2000	39.66203
2001	39.72578
2002	40.67279
2003	40.26534
2004	40.54715
2005	40.85441
2006	41.1092
2007	41.5526
2008	41.2443
2009	40.63645
2010	39.79504
2011	38.61901
2012	39.36327
2013	37.18445
2014	36.67877
2015	36.09061
2016	35.76871
2017	35.43115
2018	35.45098