Footwear is the parent rubber industry, as rubber shoes were the first commercial products made after Goodyear discovered vulcanization. There is more tradition connected with the manufacture of rubber shoes than with other products and also probably more hand work involved by nature of the product itself. As a result, the rubber footwear manufacturers have undoubtedly had more difficulty in adopting a substitute material as the setup does not lend itself well to changes and there are many more people involved in the handling operations than with most other products.