Google Books Ngram Viewer

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

1955 - 1979 1980 - 1997 1998 1999 - 2002 2003 - 2008 problem or opportunity English
1955 - 1979 1980 - 2000 2001 - 2003 2004 - 2006 2007 - 2008 threat or opportunity English
1955 - 1972 1973 - 1999 2000 - 2001 2002 - 2004 2005 - 2008 opportunity or problem English
1955 - 1981 1982 - 2000 2001 - 2002 2003 - 2007 2008 opportunity or threat English

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