Year	Number of
1990	49.03
1991	48.53
1992	48.07
1993	47.49
1994	46.86
1995	46.27
1996	45.49
1997	44.7
1998	44.52
1999	45.49
2000	45.91
2001	46.84
2002	47.87
2003	49.02
2004	51.86
2005	52.94
2006	54
2007	55.06
2008	56.39
2009	58.29
2010	59.87
2011	61.58
2012	62.85
2013	64.52
2014	66.02
2015	67.41
2016	68.87