Year	Number
1987	7.2301967039
1988	7.3242342453
1989	7.4182717867
1990	7.5123093281
1991	7.6063468695
1992	7.7003844109
1993	7.7944219523
1994	7.8884594937
1995	7.9824970351
1996	8.0765345765
1997	8.1705721179
1998	8.2646096593
1999	8.3586472008
2000	8.4526847422
2001	10.129984051
2002	11.8072833599
2003	11.8971846606
2004	11.9870859614
2005	12.0769872621
2006	12.1668885628
2007	12.2567898635
2008	12.3510140585
2009	12.4416358416
2010	12.5322576247
2011	12.6228794078
2012	12.7135011909
2013	12.804122974
2014	12.894744757
2015	12.9853665401
2016	13.0759883232
2017	13.1558028708
2018	16.0861244019
2019	16.2764486975
2020	16.2764486975