Year	Number
1971	33.27675
1972	34.14618
1976	33.86256
1978	26.87287
1980	28.61179
1981	27.85034
1982	26.55105
1983	25.64013
1984	29.50558
1985	30.97292
1987	29.63415
1988	29.375
1990	35.45975
1996	32.94044
1999	36.01364
2002	32.66742
2004	32.06028
2005	30.77576
2009	26.17273
2011	29.79713
2012	28.65004
2013	31.37579
2014	32.72581
2015	38.77644
2016	32.15018
2017	31.15842