Every retirement allowance payable during the time this

section is operative in any county to, or on account of any member of this system or of a superseded system, who has been retired for disability shall be increased by an amount equal to the product one dollar ($1) times years of service, not to exceed years, times the number in the following table: Period during which retirement became effective Multiply by On or prior to June 30, 1957 months ended June 30, 1958 1.5 months ended June 30, 1959 months ended June 30, 1960 0.5 This

section shall not be operative in any county except as follows: The board of supervisors of a county at any time and from time to time may find that economic conditions are such as to require either that this entire section, or this

section as applied to one or more categories of members in the above table be applicable in such county. The board of supervisors of such county from time to time may either rescind or modify such finding and either find that economic conditions do not require that this

section be applicable at all in such county or be applicable to a greater, lesser, or different extent than previously found. This

section or this

section as applied to one or more categories of members in the above table, as the case may be, shall be applicable in such county when and only during the time when such finding is in effect. The giving of additional retirement benefits pursuant to this

section shall create no additional contractual rights and shall not preclude the withdrawal of such benefits either by action of the board of supervisors or of the Legislature.