Year	Number of
1990	21.4
1991	21.94
1992	22.79
1993	23.3
1994	24.45
1995	25.84
1996	27.7
1997	28.93
1998	30.65
1999	32.59
2000	34.68
2001	34.11
2002	33.94
2003	34.87
2004	35.23
2005	35.27
2006	35.09
2007	34.64
2008	34.21
2009	33.07
2010	33.38
2011	33.79
2012	33.89
2013	34.65
2014	35.51
2015	36.34
2016	37.12