Year	Number
1994	18.71655
1995	19.04096
1996	19.71746
1997	19.69282
1998	19.06188
1999	19.73192
2000	19.88392
2001	20.12456
2002	20.12525
2003	20.37207
2004	20.3958
2005	20.02915
2006	19.66731
2007	19.52976
2008	19.11525
2009	18.73052
2010	18.82953
2011	18.98629
2012	19.04429
2013	18.49475
2014	18.3828
2015	18.27385
2016	17.84702
2017	17.67788
2018	17.794