Year	Number of
1990	28.03
1991	29.33
1992	30.69
1993	32.21
1994	33.84
1995	35.63
1996	37.48
1997	39.6
1998	41.32
1999	42.69
2000	42.66
2001	44.23
2002	44.83
2003	45.34
2004	44.86
2005	45.45
2006	47.22
2007	49.14
2008	51.48
2009	54.59
2010	58.52
2011	62.06
2012	65.27
2013	69.35
2014	73.28
2015	76.73
2016	80.29