Year	Number of
1990	40.69
1991	40.09
1992	40.51
1993	41.23
1994	40.6
1995	41.03
1996	39.72
1997	38.75
1998	38.08
1999	37.37
2000	38.78
2001	38.9
2002	39.29
2003	40.41
2004	40.6
2005	40.51
2006	40.6
2007	40.55
2008	39.7
2009	39
2010	38.98
2011	39.89
2012	41.12
2013	43.12
2014	45.15
2015	46.78
2016	48.46