Year	Number
1970	35.92499
1971	35.78002
1972	35.90741
1973	36.54908
1974	36.3855
1975	36.18169
1976	36.16966
1977	36.8657
1978	36.79176
1979	36.60302
1980	36.48874
1981	36.139
1982	35.71618
1983	34.45534
1984	33.98218
1985	33.52548
1986	33.15765
1987	33.12408
1988	33.19931
1989	32.61015
1990	32.80725
1991	32.70133
1992	32.72575
1993	32.60806
1994	32.62379
1995	32.36577
1996	32.40049
1997	32.07054
1998	31.90109
1999	31.80821
2000	31.84988
2001	31.8511
2002	31.59544
2003	31.72718
2004	31.7082
2005	31.82643
2006	31.48994
2007	31.29214
2008	31.30122
2009	30.65549
2010	29.92575
2011	29.28531
2012	28.94606
2013	27.60211
2014	27.46432
2015	27.0575
2016	27.77988
2017	27.61436
2018	27.85282