Year	Number of
1990	34.16
1991	34.76
1992	35.63
1993	36.29
1994	37.33
1995	37.97
1996	38.48
1997	38.98
1998	39.36
1999	38.96
2000	38.5
2001	38.18
2002	37.97
2003	37.76
2004	37.81
2005	37.76
2006	37.95
2007	38.17
2008	38.17
2009	38.17
2010	38.37
2011	38.95
2012	39.55
2013	40.03
2014	40.33
2015	40.52
2016	40.9