Section 525.9 - Criteria for employment of workers with disabilities under certificates at special minimum wage rates(a) In order to determine that special minimum wage rates are necessary in order to prevent the curtailment of opportunities for employment, the following criteria will be considered:(1) The nature and extent of the disabilities of the individuals employed as these disabilities relate to the individuals' productivity;(2) The prevailing wages of experienced employees not disabled for the job who are employed in the vicinity in industry engaged in work comparable to that performed at the special minimum wage rate;(3) The productivity of the workers with disabilities compared to the norm established for nondisabled workers through the use of a verifiable work measurement method (see § 525.12(h) ) or the productivity of experienced nondisabled workers employed in the vicinity on comparable work; and,(4) The wage rates to be paid to the workers with disabilities for work comparable to that performed by experienced nondisabled workers.(b) In order to be granted a certificate authorizing the employment of workers with disabilities at special minimum wage rates, the employer must provide the following written assurances concerning such employment:(1) In the case of individuals paid hourly rates, the special minimum wage rates will be reviewed by the employer at periodic intervals at a minimum of once every six months; and,(2) Wages for all employees will be adjusted by the employer at periodic intervals at a minimum of once each year to reflect changes in the prevailing wages paid to experienced nondisabled individuals employed in the locality for essentially the same type of work.