Year	Number of
1990	13.71
1991	14.03
1992	14.36
1993	14.72
1994	15.11
1995	15.5
1996	15.9
1997	16.29
1998	16.68
1999	17.09
2000	17.66
2001	18.95
2002	20.3
2003	21.7
2004	23.2
2005	24.85
2006	26.33
2007	28.02
2008	29.91
2009	31.95
2010	34.09
2011	35.63
2012	36.52
2013	37.4
2014	38.32
2015	39.26
2016	40.46