Year	Number of
1990	35.9
1991	37.8
1992	39.78
1993	41.86
1994	44.09
1995	46.55
1996	47.21
1997	48.06
1998	48.82
1999	49.64
2000	50.55
2001	51.97
2002	53.47
2003	55
2004	56.58
2005	58.28
2006	60.59
2007	63.13
2008	65.86
2009	68.74
2010	71.82
2011	74.32
2012	76.97
2013	79.67
2014	82.44
2015	85.33
2016	88.39