Year	Percent
1998-01-01	27.6341852895308
1999-01-01	27.9296259470860
2000-01-01	28.4167421926150
2001-01-01	28.2007230405334
2002-01-01	28.8105041509925
2003-01-01	29.5947465545253
2004-01-01	30.0921237425546
2005-01-01	30.5449655009997
2006-01-01	31.4126376905135
2007-01-01	31.6829599915482
2008-01-01	32.2555464025013
2009-01-01	32.3983633033241
2010-01-01	31.6726212637154
2011-01-01	29.5157544667169
2012-01-01	27.1291153880133
2013-01-01	25.8228868587035