Ingvar Carlsson ( born 9 November 1934 in BorÃ s , VÃ stra GÃ taland County ( then Ã lvsborg County ) , Sweden ) , is a Swedish politician , former Prime Minister of Sweden ( March 1986 â `` October 1991 ; October 1994 â `` March 1996 ) and leader of the Social Democratic Party ( March 1986 â `` March 1996 ) . GÃ sta Ingvar Carlsson ( born 9 November 1934 ) is a Swedish politician , former Prime Minister of Sweden ( 1986 â `` 1991 ; 1994 â `` 1996 ) and leader of the Swedish Social Democratic Party ( 1986 â `` 1996 ) .