Year	Number of
1990	24.8
1991	25.58
1992	25.87
1993	26.54
1994	26.68
1995	27.41
1996	27.84
1997	28.55
1998	29.26
1999	29.85
2000	30.28
2001	30.66
2002	31.89
2003	32.66
2004	33.89
2005	34.03
2006	34.52
2007	34.95
2008	35.07
2009	35.67
2010	36.99
2011	38.39
2012	38.23
2013	40.57
2014	41.31
2015	42.73
2016	43.96