Period	Percent
1970-01-01	3.07
1975-01-01	3.30
1980-01-01	3.72
1985-01-01	4.50
1990-01-01	6.12
1995-01-01	8.89
2000-01-01	10.02
2005-01-01	11.80
2010-01-01	13.13