Whenever the unencumbered balance of interest deposited in or earned by the School Employees Fund, after deducting administrative expenses paid or encumbered, exceeds two million dollars ($2,000,000) as of the close of each fiscal year, the unencumbered balance shall be credited as of the close of that fiscal year to the account of each school employer which has a positive balance in the fund, in the proportion that each positive account balance bears to the total of all positive account balances.