Google Books Ngram Viewer

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

1700 - 1751 1752 - 1771 1772 - 1788 1789 - 1957 1958 - 2000 encouragement English
1700 - 1812 1813 - 1972 1973 - 1982 1983 - 1991 1992 - 2000 incentive English

Run your own experiment! Raw data is available for download here.
© 2013 Google - Privacy & Terms - About Google - About Google Books - About Ngram Viewer