Year	Number of
1990	17.93
1991	18.38
1992	18.86
1993	19.41
1994	20.19
1995	21.43
1996	22.78
1997	24.5
1998	26.84
1999	29.17
2000	31.77
2001	33.5
2002	35.04
2003	35.67
2004	35.51
2005	34.2
2006	33.46
2007	33.14
2008	33.27
2009	32.67
2010	32.74
2011	33.23
2012	35.14
2013	36.07
2014	37.77
2015	39.68
2016	41.9