Year	Number of
1990	40.38
1991	41.14
1992	41.93
1993	42.67
1994	43.42
1995	44.11
1996	43.95
1997	43.7
1998	43.54
1999	43.23
2000	43.03
2001	43.06
2002	43.39
2003	44.04
2004	44.92
2005	45.96
2006	47.05
2007	48.25
2008	49.61
2009	51.16
2010	52.9
2011	55.07
2012	57.47
2013	60
2014	62.78
2015	65.75
2016	68.92