Year	Number
1973	37.60976
1974	38.04878
1978	27.66234
1979	22.8481
1980	28.21978
1981	30.94444
1982	29.1405
1983	31.03191
1984	28.27273
1985	29.17431
1986	26.22047
1987	24.00746
1988	19.65455
1989	19.97688
1991	18.61143
1992	18.17614
1993	17.85714
1994	18.09714
1995	18.46591
1996	18.12222
1998	17.03093
1999	16.47179
2000	14.87864
2001	14.23077
2002	13.88614
2003	14.71271
2004	15.01587
2005	14.95238
2006	15.17742
2007	14.84293
2008	14.18932
2009	15.17098
2010	12.65086
2011	16.66286
2012	17.44767
2013	15.07692
2014	16.55738
2015	17.56471
2016	16.67742
2017	16.3545
2018	18.24405