Period	Percent
1970-01-01	5.70
1975-01-01	6.90
1980-01-01	8.90
1985-01-01	11.71
1990-01-01	15.95
1995-01-01	21.10
2000-01-01	26.82
2005-01-01	31.81
2010-01-01	39.80