Year	Number of
1990	29.75
1991	30.04
1992	29.05
1993	28.62
1994	28.76
1995	28.31
1996	28.11
1997	28.66
1998	28.31
1999	28.04
2000	28.3
2001	28.98
2002	28.21
2003	27.06
2004	27.06
2005	27.22
2006	27.43
2007	27.16
2008	26.9
2009	27
2010	28.29
2011	29.18
2012	29.89
2013	30.86
2014	31.46
2015	31.7
2016	31.09