Year	Number of
1990	37.52
1991	39.06
1992	40.66
1993	42.28
1994	44.1
1995	46.16
1996	48.75
1997	51.52
1998	54.59
1999	57.65
2000	60.7
2001	64.04
2002	67.38
2003	71.17
2004	75.23
2005	79.75
2006	83.71
2007	87.98
2008	92.78
2009	97.89
2010	103.34
2011	107.93
2012	112.81
2013	117.88
2014	123.37
2015	129.35
2016	136.27