I came across a study in the Krashen book I am currently reviewing about reading. The study compared a number of different contexts and the frequency of the 1000 most common words in English in those contexts. It also compared the number of rare words (words outside of the 1000 most common list) used per 1000 words used in the context.
So for example in the study the context of adults talking to children was looked at and it was found that 95.6% of the words came from within the 1000 most common words in English. In every 1000 spoken words, 9.9 rare words were used. The point of the study was to show the importance of reading.
Here were the findings:
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