The differences between the percentages of candidates qualified to appeared for the give pairs of years are: For 1994 and 1995 = 50 - 30 = 20. For 1998 and 1999 = 80 - 80 = 0. For 1994 and 1997 = 50 - 30 = 20. For 1997 and 1998 = 80 - 50 = 30. For 1999 and 2000 = 80 - 60 = 20. Thus, the maximum difference is between the years 1997 and 1998.