Year	Number
1973	32.93774
1975	61.16576
1986	16.75298
1987	20.30414
1988	20.59067
1989	19.49301
1990	21.34411
1999	22.91105
2000	25.26632
2001	24.38304
2002	25.18844
2003	27.08822
2004	27.51324
2005	25.20614
2006	30.07132
2007	32.36025
2008	35.21611
2009	35.41945
2011	29.97769
2012	36.38433
2013	35.47984
2014	32.53683
2015	33.97072
2016	32.82755
2017	29.05177
2018	28.79899
2019	29.94822