Year	Number of
1990	27.8
1991	28.72
1992	30.34
1993	32.09
1994	33.89
1995	35.45
1996	36.4
1997	37.52
1998	39.11
1999	40.83
2000	41.6
2001	40.96
2002	40.76
2003	41.03
2004	41.24
2005	41.34
2006	40.71
2007	40.01
2008	38.8
2009	38.03
2010	38.28
2011	38.57
2012	38.73
2013	38.93
2014	39.21
2015	39.42
2016	39.77