Year	Number of
1990	28.3
1991	28.83
1992	29.59
1993	30.43
1994	31.35
1995	32.32
1996	32.61
1997	32.92
1998	33.42
1999	34.11
2000	35.06
2001	35.7
2002	36.69
2003	37.96
2004	39.2
2005	40.37
2006	41.13
2007	41.64
2008	42.65
2009	44.01
2010	45.98
2011	48.14
2012	50.93
2013	54.38
2014	57.53
2015	60.12
2016	63.07