Year	Number of
1990	21.44
1991	22.21
1992	22.98
1993	23.81
1994	24.74
1995	25.79
1996	27.03
1997	28.38
1998	29.93
1999	31.59
2000	33.39
2001	35.22
2002	37.19
2003	39.34
2004	41.62
2005	44.05
2006	46.24
2007	48.59
2008	51.19
2009	53.98
2010	56.94
2011	59.72
2012	62.7
2013	65.94
2014	69.24
2015	72.6
2016	76.17