How did henry ford effect the automobile industry?

By creating an assembly line, he made the industry more efficient, causing automobiles to be cheaper.

Henry Ford was the determined to build a simple, reliable and fair car; a car the average in American worker could afford. Out of that resolve came the Model T and the assembly line - two innovations that reform American society and molded the world we live in today.
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high entry costs prevent new producers from entering the market.

explanation:

an oligopoly is a term used to clarify the structure of a particular market, industry, or organization. a market is considered oligopolistic or amazingly focused when it is shared between a few companies.