Year	Number of
1990	26.56
1991	26.69
1992	26.83
1993	26.96
1994	27.1
1995	27.3
1996	27.37
1997	27.51
1998	27.87
1999	28.68
2000	29.22
2001	29.89
2002	30.58
2003	31.4
2004	32.87
2005	33.67
2006	34.64
2007	35.66
2008	36.88
2009	38.44
2010	39.94
2011	41.35
2012	42.57
2013	44.01
2014	45.42
2015	46.85
2016	48.27