Year	Total
1971	1690000000
1972	1850000000
1973	2040000000
1974	2240000000
1975	2470000000
1976	2520000000
1977	2901000000
1978	3336000000
1979	4186000000
1980	4206000000
1981	4951000000
1982	5901000000
1983	6151000000
1984	6851000000
1985	7646000000
1986	8502000000
1987	8502000000
1988	9002000000
1989	9502000000
1990	9402000000
1991	6407000000
1992	11510000000
1993	11790000000
1994	12070000000
1995	12340000000
1996	12620000000
1997	12900000000
1998	13170000000
1999	13450000000
2000	13690000000
2001	14580000000
2002	15450000000
2003	15880000000
2004	17110000000
2005	19190000000
2006	19970000000
2007	20440000000
2008	21720000000