Year	Number of
1990	39.44
1991	40.88
1992	42.28
1993	43.69
1994	45.14
1995	46.7
1996	47.03
1997	47.6
1998	48.24
1999	48.75
2000	49.26
2001	49.75
2002	50.28
2003	50.69
2004	51.11
2005	51.66
2006	52.25
2007	52.84
2008	53.31
2009	53.61
2010	54.03
2011	55.99
2012	58.12
2013	60.43
2014	62.77
2015	65.19
2016	67.68