Final answer:
The highest-rated search engine according to the American Customer Satisfaction Index is not detailed in the provided references. The provided materials discuss consumer confidence rather than search engine satisfaction. Latest search engine satisfaction scores can be found by consulting the American Customer Satisfaction Index.
Step-by-step explanation:
According to the American Customer Satisfaction Index, the search engine that had the highest score, 80 on a scale of 100, isn't specified in the provided references. The information from the University of Michigan surveys focuses on consumer confidence rather than search engine satisfaction. To find data specific to search engine satisfaction scores, one should refer to the latest American Customer Satisfaction Index results directly related to search engines.