Year	Measure
1971	18.87489
1972	18.71728
1973	17.75981
1974	17.01636
1975	16.48917
1976	16.0196
1977	15.01975
1978	15.70374
1979	17.2303
1980	18.00657
1981	18.88136
1982	19.60317
1983	20.37304
1984	21.30631
1985	19.82826
1986	19.82397
1987	20.256
1988	19.22903
1989	18.64013
1990	22.50111
1991	21.83814
1992	21.62727
1993	23.2567
1994	23.56077
1995	23.97492
1996	24.39348
1997	23.82887
1998	23.69647
1999	22.89602
2000	22.64894
2001	26.44094
2002	26.10033
2003	28.47882
2004	30.62001
2005	33.36501
2006	37.31102
2007	39.40721
2008	40.86079
2009	42.06459
2010	48.26535
2011	52.606
2012	57.38598
2013	64.39189
2014	69.71577