Year	Number
1973	24.06694
1979	22.34147
1980	23.75841
1983	25.97136
1985	27.73043
1986	28.90528
1987	29.08716
1988	26.77236
1989	26.12482
1990	27.43812
1998	36.31324
1999	37.41274
2000	38.4303
2001	37.49703
2002	34.36736
2003	31.07824
2004	27.37356
2005	23.92315
2006	25.04719
2007	25.24427
2008	27.0682
2009	28.16376
2010	28.33145
2011	30.62493
2012	32.23697
2013	35.20296
2016	36.192
2017	33.98251
2018	35.09524