Year	Number
1971	41.36824
1972	44.25986
1973	47.28752
1974	45.79663
1975	51.83347
1976	53.42928
1977	48.33616
1978	46.41922
1979	56.04299
1980	54.58195
1981	47.52639
1982	38.94586
1983	37.76215
1984	35.28652
1985	33.47894
1986	33.01836
1987	33.32516
1988	33.43122
1989	34.9071
1990	30.54641
1991	36.15587
1992	39.84578
1993	45.49681
1994	48.34246
1995	49.89695
1996	51.99518
1997	49.97689
1998	52.56747
1999	53.39559
2000	52.64958
2001	53.52288
2002	52.96325
2003	62.1705
2004	51.583
2005	46.8289
2006	43.62338
2008	44.55301
2009	44.86809
2010	46.3918
2011	44.20067
2012	44.14979
2013	43.72854
2014	45.92349
2015	45.04478
2016	41.63992
2017	43.56977
2018	39.19712