Google Books Ngram Viewer

Graph these comma-separated phrases:
case-insensitive
between and from the corpus with smoothing of .  
Search in Google Books:

1850 - 1925 1926 - 1960 1961 - 1967 1968 - 1996 1997 - 2008 class warfare English
1850 - 1906 1907 - 1980 1981 - 1987 1988 - 1996 1997 - 2008 progressive tax English

Run your own experiment! Raw data is available for download here.
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