Year	Number of
1990	56.1
1991	57.06
1992	58.14
1993	59.28
1994	60.59
1995	61.86
1996	62.53
1997	63.39
1998	64.59
1999	66.71
2000	68.86
2001	71.08
2002	73.33
2003	75.74
2004	78.37
2005	81.19
2006	85.83
2007	90.88
2008	96.46
2009	102.51
2010	109.08
2011	114.63
2012	120.61
2013	127.02
2014	134.04
2015	141.8
2016	149.6