Year	Number of
1990	16.14
1991	16.89
1992	17.72
1993	18.61
1994	19.58
1995	20.64
1996	21.78
1997	23.04
1998	24.42
1999	25.9
2000	27.51
2001	29.13
2002	30.88
2003	32.79
2004	34.84
2005	37.1
2006	38.65
2007	40.28
2008	42.04
2009	43.88
2010	45.85
2011	47.77
2012	49.81
2013	51.92
2014	54.16
2015	56.52
2016	59