Year	Number of
1990	100.01
1991	103.03
1992	105.45
1993	108.04
1994	111.12
1995	116.01
1996	120.08
1997	126.09
1998	133.58
1999	142.75
2000	150.12
2001	157.7
2002	167.06
2003	178.69
2004	188.4
2005	196.33
2006	203
2007	206.44
2008	211.51
2009	214.33
2010	215.29
2011	214.64
2012	215.13
2013	216.79
2014	218.8
2015	220.88
2016	221.5