Year	Number of
1990	14.38
1991	14.97
1992	16.06
1993	16.58
1994	17.1
1995	18.29
1996	19.84
1997	20.34
1998	21.33
1999	22.59
2000	24.03
2001	25.07
2002	26.6
2003	27.25
2004	27.95
2005	28.23
2006	28.77
2007	29.28
2008	29
2009	29.47
2010	29.65
2011	30.27
2012	30.42
2013	30.14
2014	29.73
2015	30.32
2016	30.96