Year	Number of
1990	31.74
1991	32.27
1992	32.94
1993	33.04
1994	32.45
1995	32.23
1996	31.93
1997	32.48
1998	32.95
1999	34.41
2000	35.9
2001	36.4
2002	36.88
2003	37.88
2004	39.19
2005	40.03
2006	40.15
2007	40.14
2008	40
2009	40.03
2010	40.03
2011	41.87
2012	43.02
2013	42.25
2014	41.49
2015	41.11
2016	41.39