| | | | | | | | | | | | | | | | | | | | 1978 | | | | | | 20 | | | | | | | | | | | | | | 1987 | | 1988 | | | 20 | | | 1997 | | | | | | 2002 | | ; | | | | | | | 50% | 60% | 70% 80% | | 90% | | | | | | | | | | | | | | | | | | | | | | | | | | | | ; | | | | | | | | | | | | | | | | | | | | | | | | 40 | | | | | | | | | | | | | | | | | 2000 | | | | 2012 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |