U.S. Patents Granted, Patents Granted,
Logarithmic Plot, pg 106.
The patents used in this chart are, as described
by the U.S. Patent and Trademark Office, “patents
for inventions,” also known as “utility”
patents. The U.S. Patent and Trademark Office, Table of
Annual U.S. Patent Activity, http://www.uspto.gov/web/offices/ac/ido/oeip/taf/h_counts.htm.