Year	Number
1994	16.05988
1995	16.38796
1996	15.67625
1997	16.58482
1998	18.02668
1999	16.86133
2000	17.53709
2001	18.81247
2002	18.87955
2003	18.10024
2004	18.31285
2005	18.07911
2006	17.89823
2007	17.09831
2008	16.72704
2009	16.49911
2010	16.53015
2011	16.78628
2012	16.76984
2013	19.38848
2014	19.38665
2015	18.89385
2016	18.35134
2017	18.06642
2018	17.97541