Final answer:
It is not possible to determine the percentage required for a business to rely on the industry practice safe haven without specific information about independent contractors in the industry.
Step-by-step explanation:
The question is asking what percentage of a particular industry must have a practice of using independent contractors for a business to rely on the industry practice safe haven. Unfortunately, the information provided does not give us a specific percentage for independent contractors in any industry. Therefore, without this specific information, it is not possible to determine the percentage required for a business to rely on the industry practice safe haven.