Year	Number
1993	22.10757
1994	22.39318
1995	21.97551
1998	19.30652
1999	18.76821
2000	17.57749
2001	19.70391
2002	19.11084
2003	18.39264
2004	17.67725
2005	17.50733
2006	17.20096
2007	15.34656
2008	16.61387
2009	15.71918
2010	15.24042
2011	15.07841
2012	14.94005
2013	15.04676
2014	15.23635
2015	15.24933
2016	15.2188
2017	15.53919