All contributions and deposits shall bear simple interest at a rate to be fixed by the board of retirement with the approval of the board of supervisors, not to exceed 4 percent a year.
Interest shall be credited semiannually on June 30th and December 31st to all contributions in the retirement fund to the credit of each member which have been on deposit for six months immediately prior to such date.
(Added by Stats. 1947, Ch. 424.)