Year	Number of
1990	38.17
1991	36.63
1992	34.77
1993	32.74
1994	30.8
1995	29.21
1996	27.61
1997	27.1
1998	26.38
1999	25.14
2000	24.73
2001	24.17
2002	23.61
2003	23.56
2004	23.68
2005	23.91
2006	23.83
2007	23.79
2008	23.82
2009	23.99
2010	24.38
2011	24.74
2012	25.26
2013	25.78
2014	26.32
2015	26.87
2016	27.45