Year	Number of
1990	33.64
1991	32.99
1992	33.16
1993	32.12
1994	32.72
1995	31.84
1996	29.01
1997	29.23
1998	32.48
1999	32.92
2000	35.72
2001	35.7
2002	36.06
2003	36.12
2004	36.91
2005	35.89
2006	36.52
2007	35.19
2008	34.63
2009	35.16
2010	35.22
2011	35.07
2012	35.36
2013	37.01
2014	37.57
2015	38.61
2016	39.59