Beginning on July 1, 1991 and thereafter, each county board of education shall deposit in the member's annuity account created pursuant to section nine of this article an amount equal to seven and one-half percent of all compensation paid to members of the defined contribution system in excess of that authorized for minimum salaries in sections two and eight-a, article four, chapter eighteen-a of this code to the extent that the excess exceeds the amount distributed for salary equity to the county.