Year	Number of
1990	25.31
1991	25.26
1992	25.05
1993	24.66
1994	25.36
1995	25.88
1996	27.75
1997	29.55
1998	31.55
1999	33.59
2000	36.5
2001	37.75
2002	39.94
2003	40.1
2004	41.65
2005	43.06
2006	45.24
2007	48.23
2008	51.25
2009	54.31
2010	57.25
2011	59.76
2012	62.09
2013	64.47
2014	66.66
2015	69.04
2016	71.75