Year Thousands of Persons 1990-01-01 3.7 1991-01-01 3.8 1992-01-01 3.8 1993-01-01 4.3 1994-01-01 4.3 1995-01-01 4.0 1996-01-01 2.6 1997-01-01 3.5 1998-01-01 3.9 1999-01-01 4.0 2000-01-01 4.2 2001-01-01 4.1 2002-01-01 3.9 2003-01-01 4.1 2004-01-01 4.3 2005-01-01 4.0 2006-01-01 4.0 2007-01-01 4.0 2008-01-01 4.0 2009-01-01 3.6 2010-01-01 3.6 2011-01-01 3.6 2012-01-01 3.6 2013-01-01 3.5 2014-01-01 3.5 2015-01-01 3.6 2016-01-01 3.6 2017-01-01 3.5