Year	Number of
1990	23.86
1991	25.26
1992	26.48
1993	27.7
1994	29.02
1995	30.4
1996	31.86
1997	33.23
1998	34.65
1999	36.27
2000	37.94
2001	39.63
2002	41.47
2003	43.44
2004	45.36
2005	47.61
2006	49.62
2007	52.17
2008	54.76
2009	57.3
2010	59.81
2011	62.32
2012	64.98
2013	67.39
2014	69.91
2015	72.88
2016	75.92