Year	Number of
1990	25.03
1991	26.06
1992	27.27
1993	26.88
1994	28.02
1995	28.8
1996	29.76
1997	30.48
1998	32.2
1999	34.76
2000	37.62
2001	39.74
2002	41.64
2003	44.64
2004	45.58
2005	48.02
2006	49.89
2007	51.35
2008	51.95
2009	54.37
2010	54.91
2011	56.09
2012	57.31
2013	60.61
2014	63.1
2015	63.24
2016	64.04