Year Thousands of Persons 1990-01-01 0.8 1991-01-01 0.8 1992-01-01 0.7 1993-01-01 0.6 1994-01-01 0.5 1995-01-01 0.5 1996-01-01 0.5 1997-01-01 0.5 1998-01-01 0.5 1999-01-01 0.5 2000-01-01 0.5 2001-01-01 0.7 2002-01-01 0.7 2003-01-01 0.5 2004-01-01 0.5 2005-01-01 0.4 2006-01-01 0.4 2007-01-01 0.4 2008-01-01 0.3 2009-01-01 0.3 2010-01-01 0.3 2011-01-01 0.4 2012-01-01 0.4 2013-01-01 0.3 2014-01-01 0.3 2015-01-01 0.2 2016-01-01 0.2 2017-01-01 0.1