Year	Number of
1990	22.25
1991	22.92
1992	23.83
1993	24.83
1994	25.88
1995	26.75
1996	27.07
1997	26.96
1998	26.64
1999	26.82
2000	27.05
2001	28.45
2002	29.89
2003	30.91
2004	31.33
2005	31.85
2006	32.69
2007	33.05
2008	35.02
2009	38.83
2010	40.79
2011	42.39
2012	44.82
2013	48.35
2014	52.21
2015	55.95
2016	59.92