Year	Number of
1990	40.38
1991	39
1992	39.05
1993	38.21
1994	37.17
1995	36.48
1996	36.38
1997	35.38
1998	34.08
1999	33.5
2000	32.29
2001	31.12
2002	30.63
2003	30.43
2004	29.82
2005	29.31
2006	28.78
2007	28.54
2008	28.27
2009	28.62
2010	29.11
2011	29.01
2012	28.44
2013	28.09
2014	29.61
2015	30.3
2016	30.9