text: This analysis was revised when it was determined that the interim program , which began on January 1 , 1995 , would last 30 months rather than 18 months and there were changes in the estimated cost of deposit control testing and the addition , in the final rule , of a required deposit demonstration test to qualify test fuels for certification testing purposes .
  
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  The interim program 's length changed due to unpredictable factors out of their control .