Year	Percent
1977-01-01	43.9560984509232
1978-01-01	42.1101591967253
1979-01-01	40.8534326374945
1980-01-01	40.0836302076235
1981-01-01	39.2579672298986
1982-01-01	38.5086078942976
1983-01-01	38.0550198582623
1984-01-01	37.0814990839372
1985-01-01	35.8893585293690
1986-01-01	34.8760462764970
1987-01-01	33.9404435681224
1988-01-01	33.2313513387026
1989-01-01	32.2491715959263
1990-01-01	32.1646659142143
1991-01-01	32.2522246599569
1992-01-01	31.5927650204259
1993-01-01	31.4081682400262
1994-01-01	30.5570162578792
1995-01-01	30.2779752416975
1996-01-01	29.8820185053095
1997-01-01	29.2903003266954
1998-01-01	29.2935919631723
1999-01-01	29.2677670457407
2000-01-01	29.2852410089826
2001-01-01	29.5961084150790
2002-01-01	29.9461227437493
2003-01-01	30.3261474552693
2004-01-01	30.8306097475098
2005-01-01	30.8229584825998
2006-01-01	30.7023926346379
2007-01-01	30.9311568237129
2008-01-01	30.7054569512140
2009-01-01	30.9730920792459
2010-01-01	31.6041682667003
2011-01-01	32.1882506830453
2012-01-01	32.4203188512383
2013-01-01	32.8353961134792
2014-01-01	32.8837862821895
2015-01-01	33.0629603079112
2016-01-01	32.6953917045613
2017-01-01	32.1100454111843