Year	Number
1971	27.46795
1972	28.48777
1973	28.68685
1974	25.42822
1975	25.9537
1976	25.9673
1977	27.14149
1978	25.19196
1979	25.96293
1980	27.20988
1981	24.3794
1983	23.31442
1984	24.95398
1985	25.29549
1986	24.47701
1987	28.7471
1989	28.29224
1990	31.05711
1991	31.30468
1992	31.51773
1993	30.46101
1994	33.39804
1995	33.60267
1996	30.23628
1997	30.38237
1998	32.83094
1999	36.95683
2000	37.44125
2001	38.68007
2002	37.98627
2003	39.40341
2004	38.53397
2005	36.56464
2006	38.47812
2007	35.15646
2008	34.36475
2010	37.48167
2011	37.61854
2012	33.86525
2013	36.13171
2014	44.68514
2015	37.14288
2017	38.67589
2018	36.13813