Period	Percent
1970-01-01	5.41
1975-01-01	6.30
1980-01-01	7.14
1985-01-01	8.10
1990-01-01	9.90
1995-01-01	11.87
2000-01-01	11.02
2005-01-01	9.60
2010-01-01	9.41