Year	Number of
1990	25.66
1991	28.23
1992	30.67
1993	33.02
1994	34.72
1995	35.59
1996	37.2
1997	39.24
1998	41.36
1999	43.34
2000	45.16
2001	46.58
2002	48.37
2003	51.82
2004	56.75
2005	60.65
2006	63.9
2007	67.5
2008	70.74
2009	73.69
2010	76.12
2011	78.28
2012	80.47
2013	82.65
2014	84.84
2015	87.04
2016	88.74