Year	Number
1973	8.15796
1993	16.33821
1994	17.32597
1995	17.93981
1997	19.89764
1998	21.17881
2001	9.28495
2002	9.60172
2003	9.6575
2004	9.69381
2005	10.19018
2006	9.67494
2007	9.88362
2013	5.99969
2014	5.51507
2015	5.63498
2016	5.55522
2017	5.51912