Period	Percent
1970-01-01	3.10
1975-01-01	4.88
1980-01-01	9.40
1985-01-01	8.15
1990-01-01	7.30
1995-01-01	6.97
2000-01-01	7.38
2005-01-01	9.02
2010-01-01	10.67