Year	Number
1983	27.46508
1984	27.58919
1985	27.16234
1986	26.73469
1987	26.64986
1988	26.59925
1989	26.26093
1990	25.88464
1991	25.42381
1992	25.0689
1993	24.07739
1994	23.70537
1995	23.4412
1996	23.27167
1997	23.1301
1998	23.61572
1999	22.1405
2000	21.93549
2001	22.18436
2002	22.25734
2003	22.52732
2004	22.85002
2005	23.91
2006	23.41863
2007	23.0406
2008	23.47137
2009	23.49548
2010	22.20105
2011	23.34061
2012	24.25326
2013	24.16213
2014	23.48068
2015	23.98509
2016	24.43605
2017	25.25039
2018	24.10295