Year	Number of
1990	20.25
1991	20.92
1992	21.68
1993	22.33
1994	23.71
1995	24.84
1996	24.97
1997	25.54
1998	25.94
1999	26.25
2000	26.55
2001	27.17
2002	27.83
2003	28.35
2004	29.83
2005	31.05
2006	31.9
2007	32.27
2008	33.92
2009	34.75
2010	36.05
2011	37.11
2012	38.17
2013	39.6
2014	40.37
2015	41.56
2016	42.74