Year	Number of
1990	24.18
1991	24.94
1992	25.5
1993	26.31
1994	26.71
1995	27.56
1996	27.92
1997	28.61
1998	30.67
1999	31.71
2000	32.52
2001	33.17
2002	32.88
2003	33.01
2004	33.41
2005	33.8
2006	34.38
2007	35.04
2008	35.69
2009	36.24
2010	37.23
2011	38.01
2012	39.02
2013	40.22
2014	41.81
2015	42.76
2016	44.78