Year	Number of
1990	34.2
1991	34.8
1992	35.45
1993	36.08
1994	36.69
1995	37.28
1996	37.52
1997	37.67
1998	37.79
1999	37.88
2000	38
2001	38.29
2002	38.65
2003	39.05
2004	39.44
2005	39.91
2006	40.08
2007	40.1
2008	40.02
2009	39.93
2010	39.92
2011	40.15
2012	40.53
2013	40.81
2014	41.12
2015	41.46
2016	42.17