Year	Number of
1990	25.82
1991	26.52
1992	27.07
1993	27.6
1994	28.71
1995	29.77
1996	31.15
1997	32.34
1998	33.66
1999	35.09
2000	36.64
2001	37.2
2002	37.16
2003	37.59
2004	37.77
2005	37.66
2006	36.95
2007	35.88
2008	35.3
2009	34.69
2010	33.76
2011	34.2
2012	34.48
2013	34.67
2014	35.19
2015	35.84
2016	36.34