Period	Percent
1970-01-01	2.44
1975-01-01	4.40
1980-01-01	7.21
1985-01-01	11.51
1990-01-01	17.04
1995-01-01	20.05
2000-01-01	24.80
2005-01-01	21.34
2010-01-01	30.89