Year	Number
1986	12.86825
1987	12.99848
1988	13.07169
1989	13.29281
1990	13.31626
1991	12.44236
1992	12.7696
1993	13.66289
1994	13.97001
1995	13.88699
1996	13.82041
1997	14.22655
1998	15.06277
1999	15.68657
2000	15.61228
2001	15.66077
2002	15.65737
2003	15.26224
2004	16.08386
2005	15.8452
2006	16.57616
2007	16.46718
2008	16.5541
2009	15.48769
2010	15.49629
2011	15.62865
2012	15.42068
2013	15.3558
2014	15.48008
2015	15.66196
2016	15.88248
2017	15.8979
2018	16.25409