Year	Number
1980	27.1067145233
1981	27.7928740261
1982	28.4790335288
1983	29.1651930316
1984	29.8513525344
1985	30.5375120371
1986	31.0274008579
1987	31.5172896787
1988	32.0071784995
1989	32.4970673203
1990	32.9869561411
1991	33.6601593277
1992	34.3333625142
1993	32.7772038869
1994	31.2210452596
1995	29.6648866322
1996	28.1087280049
1997	26.5525693776
1998	27.2435729085
1999	27.9345764393
2000	28.6255799702
2001	28.4745688523
2002	28.3235577344
2003	28.6427966967
2004	28.9620356591
2005	29.2812746214
2006	28.2062505471
2007	27.1312264729
2008	25.089731244
2009	24.9236627856
2010	25.0179462488
2011	26.390615425
2012	24.567101462
2013	23.7739648078
2014	23.8965245557
2015	24.6134990808
2016	23.1427821063
2017	23.5892497593
2018	23.5690486825
2019	22.9992818436
2020	22.9992818436