Year	Number of
1990	33.25
1991	34.14
1992	34.1
1993	36.46
1994	37.5
1995	39.54
1996	41.38
1997	41.89
1998	42.47
1999	43.86
2000	45.25
2001	46.44
2002	49.28
2003	52.58
2004	57.02
2005	60.98
2006	62.56
2007	63.5
2008	65.92
2009	67.96
2010	70.58
2011	72.94
2012	74.95
2013	76.3
2014	78.02
2015	79.78
2016	81.6