(Households as of March of the following year) Shares of aggregate income Year 1999 1998 1997 1996 1995 1994 1993 1992 1991 1990 1989 1988 1987 1986

Scroll down to Tabel H2 and select "all races". Calculate the percentage change in the Shares of Household Income of Quintiles between 1968 and 2008. notice the dates are in reverse chronological order. Why do you think it had changed in the manner it has?Any help would be appreciated.Thanks