Year	Total
1971	31.02
1972	32.67
1973	32.67
1974	34.05
1975	34.29
1976	35.7
1977	34.29
1978	35.7
1979	37.32
1980	38.71
1981	38.95
1982	40.36
1983	40.36
1984	40.36
1985	41.98
1986	41.98
1987	41.98
1988	43.39
1989	43.39
1990	43.39
1991	43.39
1992	43.63
1993	45.01
1994	45.01
1995	46.66
1996	48.05
1997	48.45
1998	48.86
1999	49.31
2000	49.77
2001	50.12
2002	50.34
2003	50.24
2004	50.65
2005	50.86
2006	51.28
2007	51.79
2008	52.17
2009	52.38