Year	Number of
1990	109.26
1991	110.3
1992	113.74
1993	119.74
1994	124.14
1995	127.08
1996	129.98
1997	130.78
1998	132.17
1999	134.02
2000	138.49
2001	140.04
2002	146.27
2003	146.01
2004	149.62
2005	151.67
2006	151.93
2007	154.12
2008	155.63
2009	159.44
2010	163.58
2011	164.57
2012	167.02
2013	169.46
2014	172.24
2015	175.07
2016	177.7