Period	Percent
1970-01-01	7.20
1975-01-01	8.34
1980-01-01	10.80
1985-01-01	14.18
1990-01-01	16.98
1995-01-01	19.87
2000-01-01	22.32
2005-01-01	25.10
2010-01-01	28.82