Year	Measure
1960	0.257
1961	0.2774
1962	0.2803
1963	0.292
1964	0.2982
1965	0.2884
1966	0.2784
1967	0.292
1968	0.2982
1969	0.3685
1970	0.6029
1971	0.6481
1972	0.7068
1973	0.8923
1974	0.9118
1975	0.8802
1976	0.9264
1977	0.9851
1978	1.011
1979	1.084
1980	1.163
1981	1.164
1982	1.271
1983	1.323
1984	1.362
1985	1.319
1986	1.368
1987	1.378
1988	1.451
1989	1.452
1990	1.419
1991	1.405
1992	1.426
1993	1.464
1994	1.465
1995	1.505
1996	1.519
1997	1.641
1998	1.754
1999	1.868
2000	1.943
2001	1.992
2002	2.092
2003	2.104
2004	2.094
2005	2.034
2006	2.083
2007	2.361
2008	3.439
2009	3.346
2010	3.382
2011	3.315