Year	Number of
1990	39.54
1991	39.19
1992	38.79
1993	38.46
1994	38.08
1995	37.94
1996	38.54
1997	37.3
1998	37.02
1999	39.8
2000	43.5
2001	43.35
2002	45.8
2003	48.5
2004	52.38
2005	54.17
2006	57.84
2007	60.17
2008	63.18
2009	69.49
2010	71.97
2011	75.89
2012	78.35
2013	80.55
2014	85.1
2015	89.19
2016	92.69