Period	Percent
1970-01-01	5.20
1975-01-01	7.59
1980-01-01	10.52
1985-01-01	14.15
1990-01-01	17.55
1995-01-01	20.89
2000-01-01	24.43
2005-01-01	26.81
2010-01-01	30.00