Year	Number
1980	14.92513
1993	13.38308
1994	13.43428
1995	13.73243
1996	13.65073
1997	13.64188
1998	13.5151
1999	13.49563
2000	13.28895
2001	13.28175
2002	13.56578
2003	13.83095
2004	13.58666
2005	13.1291
2006	12.80857
2007	12.54593
2008	12.07044
2009	11.83583
2010	11.70739
2011	12.36341
2012	12.37093
2013	12.72895
2014	12.76702
2015	12.545
2016	12.36689
2017	12.71581
2018	12.66168