Year	Number of
1990	25.11
1991	25.34
1992	24.98
1993	24.21
1994	23.28
1995	22.35
1996	24.15
1997	26.53
1998	29.6
1999	33.13
2000	37.04
2001	40.32
2002	43.79
2003	47.65
2004	51.85
2005	56.54
2006	61.34
2007	66.8
2008	73.19
2009	80.57
2010	89.06
2011	96.04
2012	104.11
2013	112.89
2014	122.24
2015	131.94
2016	142.97