Year	Number
1971	37.94375
1972	33.70475
1973	35.22672
1974	36.81806
1977	32.00474
1978	32.16066
1979	31.4375
1980	31.89097
1981	23.29381
1982	23.34079
1983	23.17277
1984	22.27742
1985	22.71296
1987	21.87942
1988	22.61911
1990	25.13761
1992	26.73967
1993	26.88929
1994	26.37383
1995	26.37093
1996	24.27733
1997	26.55239
1998	25.94412
1999	22.95528
2000	20.32412
2001	20.88105
2003	18.69144
2004	17.67486
2005	18.23894
2007	15.76693
2008	22.55772
2009	17.09157
2010	16.05523
2013	14.79771
2014	14.48004
2015	16.99747
2016	15.45199
2017	16.18269
2018	16.35068