Year	Number of
1990	0.99
1991	1
1992	1.02
1993	1.04
1994	1.07
1995	1.1
1996	1.12
1997	1.15
1998	1.19
1999	1.16
2000	1.12
2001	1.14
2002	1.09
2003	1.1
2004	1.09
2005	1.17
2006	1.23
2007	1.31
2008	1.42
2009	1.48
2010	1.56
2011	1.65
2012	1.75
2013	1.84
2014	1.93
2015	2.02
2016	2.07