Year	Number
1972	36.09767
1973	37.25394
1974	29.5646
1975	28.33176
1976	23.26233
1977	24.82491
1978	27.70361
1979	30.33836
1980	31.29177
1981	18.29865
1982	22.49192
1983	26.27813
1984	26.68
1985	27.06247
1986	24.78995
1987	28.04748
1988	29.00544
1989	29.57492
1990	31.05447
1991	31.41475
1992	33.7239
1993	34.60115
1994	32.014
1995	32.36461
1996	31.0387
1999	31.707
2000	30.21542
2001	33.09243
2003	34.68746
2008	40.58462
2009	36.90163
2010	31.97247
2011	29.70178
2012	29.56574
2013	29.1808
2014	28.84049
2015	28.57148
2016	28.90357
2017	28.82411
2019	28.2567