Period	Percent
1970-01-01	2.14
1975-01-01	4.10
1980-01-01	6.70
1985-01-01	7.88
1990-01-01	10.99
1995-01-01	12.09
2000-01-01	12.46
2005-01-01	13.40
2010-01-01	16.18