Year	Number of
1990	30.81
1991	31.46
1992	32.3
1993	33.07
1994	33.9
1995	34.99
1996	35.93
1997	37
1998	38.08
1999	39.09
2000	39.67
2001	40.72
2002	41.44
2003	42.86
2004	43.85
2005	44.58
2006	45.4
2007	45.99
2008	46.88
2009	48.33
2010	49.87
2011	51.39
2012	52.97
2013	54.56
2014	55.94
2015	56.57
2016	58.37