Year	Number of
1990	14.66
1991	14.97
1992	14.65
1993	14.15
1994	14.74
1995	15.69
1996	17.58
1997	17.74
1998	19.29
1999	19.95
2000	21.48
2001	22.82
2002	23.47
2003	24.22
2004	24.45
2005	24.47
2006	24.63
2007	24.74
2008	24.93
2009	25.07
2010	25.05
2011	24.72
2012	24.45
2013	24.22
2014	23.84
2015	23.24
2016	23.17