Year	Number of
1990	28.45
1991	29.24
1992	30.6
1993	32.03
1994	33.52
1995	34.87
1996	35.61
1997	36.56
1998	38.04
1999	39.66
2000	40.41
2001	39.86
2002	39.84
2003	40.28
2004	40.68
2005	40.95
2006	40.49
2007	39.91
2008	38.99
2009	38.47
2010	38.83
2011	39.21
2012	39.49
2013	39.85
2014	40.24
2015	40.59
2016	41.12