Year	Number of
1990	159.22
1991	146.11
1992	139.29
1993	134.35
1994	127.53
1995	121.88
1996	118.34
1997	115.02
1998	109.71
1999	109.78
2000	109.47
2001	111.09
2002	113.63
2003	117.17
2004	124.06
2005	129.18
2006	130.91
2007	132.93
2008	133.72
2009	134.86
2010	137.67
2011	143.65
2012	150.63
2013	160.66
2014	170.59
2015	179.29
2016	189.74