Year	Number of
1990	54.17
1991	57.54
1992	60.58
1993	63.54
1994	66.68
1995	70.26
1996	74.68
1997	79.87
1998	85.6
1999	91.91
2000	98.71
2001	103.73
2002	109.06
2003	114.67
2004	120.63
2005	126.98
2006	130.4
2007	133.94
2008	137.89
2009	142.15
2010	146.8
2011	151.09
2012	155.89
2013	161.09
2014	166.58
2015	172.31
2016	178.55