Period	Percent
1970-01-01	2.45
1975-01-01	3.40
1980-01-01	4.50
1985-01-01	5.56
1990-01-01	7.01
1995-01-01	8.35
2000-01-01	9.36
2005-01-01	9.00
2010-01-01	12.09