Interestingly, according to the Google Ngram search, the phrase "I know" has also had an uptick since the 1980's.[1] [1] https://books.google.com/ngrams/graph?

Interestingly, according to the Google Ngram search, the phrase "I know" has also had an uptick since the 1980's.[1] [1] https://books.google.com/ngrams/graph?content=I+know&case_insensitive=on&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2CI%20know%3B%2Cc0 https://books.google.com/ngrams/graph?content=I+know&case_in...