Year	Number
1983	14.19484
1984	14.18662
1985	14.30207
1986	14.40356
1987	14.65411
1988	14.85117
1989	15.06019
1990	15.31543
1991	15.53164
1992	15.77224
1993	16.08373
1994	16.06418
1995	16.17686
1996	16.0729
1997	15.96812
1998	15.853
1999	15.56107
2000	15.19476
2001	15.59849
2002	15.02581
2003	15.0115
2004	14.44503
2005	14.35163
2006	14.05834
2007	14.04042
2008	13.93131
2009	14.10519
2010	13.83688
2011	14.49486
2012	14.62766
2013	14.65794
2014	14.73938
2015	14.66827
2016	14.5456
2017	14.42705
2018	14.42524