Year	Number of
1990	26.82
1991	27.04
1992	27.79
1993	28.58
1994	29.63
1995	29.92
1996	29.91
1997	30.04
1998	32.91
1999	34.83
2000	40.32
2001	40.57
2002	42.29
2003	45.95
2004	46.53
2005	47.67
2006	47.54
2007	48.63
2008	51.61
2009	52.01
2010	53.87
2011	53.07
2012	53.71
2013	54.58
2014	54.26
2015	53.87
2016	53.23