Low

Medium-low

Medium-high

High

1987-1990

46.43

8.57

14.45

6.69

1991-1995

44.11

10.07

15.16

10.48

1996-2000

35.63

12.09

19.04

16.26

2001-2005

27.52

11.48

21.67

26.53

2006-2011

21.82

14.25

26.71

28.53