Year	Number of
1990	22.55
1991	24.29
1992	25.02
1993	25.4
1994	25.43
1995	26.38
1996	26.11
1997	27.27
1998	26.88
1999	26.99
2000	26.46
2001	27.41
2002	27.42
2003	27.59
2004	26.37
2005	27.55
2006	28.31
2007	30.41
2008	31.75
2009	32.54
2010	34.94
2011	35.32
2012	36.21
2013	37.17
2014	38.19
2015	39.23
2016	40.33