Government Interest in US Patents

Classifications most often cited

José A. Montalvo, PhD
April 2005


Patents filed with the United States Patent office (USPTO) may contain a field labeled “Government Interest”. This field contains data that indicates any interest or rights that the US government may have on a particular patent. This interest may arise for several reasons. For example, the inventor may be an employee of a US government agency, or its armed forces. The invention may have come about as a result of research funded by a grant, or special funding by the government was provided. Although the number of patents that indicate government interest is small, they are interesting in that they reveal specific areas of scientific and technological development where the United States government has invested millions of dollars. Essentially, this is taxpayer funded research.

The relationship between research, development and patenting is well understood. Patents represent the intellectual capital of a nation, and most nations understand the need to stimulate and protect this wealth. Thus, they create the legal structures to protect the new developments and improvements of innovators and scientists. In the United States this is done through the laws that regulate Patents, Trademarks, and Copyrights. The patent laws of the United States allow the government to benefit from new patents through the use of Government Interest.

How many of these patents exist?

Our dataset contains all of the patents for the years 1976 to 2003. A total of 2,992,116 patents of all types were analyzed: Design, Plant, Utility, SIR’s, Reissue, and Defensive Publication patents. Of these, 56,624 contained a field indicating government interest in them. Although this number represents only 0.0189% of all the patents in the set, the number of these patents continues to grow. Click on the attached chart for an illustration of that growth.

Contents of the Government Interest Field

The field that indicates government interest is very similar for many patents. Most often the legal boilerplate states the inventor’s desire to make the patent available to the government for any purpose it deems necessary. An example of this type of field is:

“The invention described herein may be manufactured, used and licensed by or for the United States Government without payment to me of any royalty thereon.”

Exempting the government from payment of royalties is a major theme of these statements. Needless to say this is a direct economic benefit to the government, although the invention may have been the direct result of a government employee’s work. Thus we find the following in many of these patents:

“The invention described herein was made by an employee of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefore.”

Often the content of the field is more specific about the activities that led to the invention, even if there is doubt as to the claim the government might in fact have on the patent. For such patents we see:

“The present invention has been made under a contract by the United States Air Force Office of Scientific Research and the Microgravity Science and Applications Division of NASA and the government may have certain rights to the subject invention.”

Another group of patents is more specific as to the source of funding that led to the invention:

“The U.S. government owns rights in the present invention pursuant to NIH Grant CA-28149 and NIH Grant CA54168.”

The scope of government rights may vary in some cases:

“Part of the work performed during development of this invention utilized U.S. Government funds under National Cancer Institute grants (R37 CA36401, Leukemia Program Project Grant CA20180, and Cancer Center Grant CA21765). The U.S. Government has certain rights in this invention.”

What is a Classification?

The patent classification system is the primary organizational scheme for all inventions registered through the patenting system of United States. They provide a key to understanding the underlying technology of the invention that has been patented. The following two excerpts from “Overview of the Classification System”, a publication of the U.S. Patent Office, provide the description and rationale of the system.

“The United States Patent Classification System(USPC) divides the entire set of U.S. patents into searchable collections based on the technology claimed in the patents. The primary groupings of patents in USPC are called classes. Utility classes are based on (1) technology associated with a particular industry, or (2) subject matter having similar function, use, or structure. Design classes are based on ornamental appearance. Plants are provided for in a single Plant class.”

“Because claims define the novel disclosure(s) in a patent, each claim is assigned a classification. These are considered mandatory classifications (a claim that recites plural embodiments of an invention may require plural mandatory classifications). Once all the claims have been classified, one of the mandatory classifications is selected as the “original” (OR) classification. The OR classification is an administrative tool used by USPTO (1) to assign applications to a particular organizational unit for examination, and (2) to aid in USPC reclassification.”

From Overview of the Classification System at

In addition, patents have subclassifications that further define the technology of the invention. That aspect is not covered by this paper.


To find the data for our analysis, we wrote some Java code (see Appendix B) that looked into each patent in our set that had a Government Interest field, and extracted the classification(s) listed for that patent. A hash table was used to collect the class numbers and count them. This was done for each complete year in our set (1976- 2003). The results were then plugged into Excel spreadsheets to obtain the graphs and statistics provided herein.

Most Often Cited Classifications

Our research has found that the number of classifications cited for patents that contain claims of government interest is actually quite limited. The conclusion is that there are certain areas that the government is most interested in. We sought the ten most cited classifications for the years 1976 to 2003. The classifications and their percentage are as follows:

Class Total Patents with this Class Percentage of this Class
435 7,542 13.31%
514 4,238 7.48%
424 3,794 6.70%
536 3,766 6.65%
530 3,540 6.25%
250 3,743 6.13%
73 2,847 5.02%
436 1,756 3.10%
364 1,539 2.71%
356 1,398 2.46%

What do these classification numbers represent?

The following are the textual descriptions of the most cited classifications, and the hyperlink to the pages that describe their subclasses. The list is in order of citation frequency.
435 Chemistry: molecular biology and microbiology
514 Drug, bio-affecting and body treating compositions
424 Drug, bio-affecting and body treating compositions
536 Organic compounds
530 Chemistry: natural resins or derivatives; peptides or proteins; lignins or reaction products thereof
250 Radiant energy
73 Measuring and testing
436 Chemistry: analytical and immunological testing
364 Not listed
356 Optics: measuring and testing


The top ten classifications make up over 60% of all classifications cited. Of those, the top six account for over 46% of all cited classifications. (See Appendix D, for a scatter graph of citation frequency) Most of the cited classification numbers range between class 204 and class 438. (See Appendix C, a scatter graph of classifications for the entire set) Of the most cited classes, six are related to areas of molecular biology, microbiology, development of drugs and pharmaceuticals, organic compounds and chemistry. The remaining four are classes dealing with energy, optics, and testing and measurement.

A tentative conclusion is that these results point to the United States Government’s interest and desire to stimulate research and development in these particular areas. Further research into what subclassifications accompany these main classes is warranted. Knowing the subclasses for these patents would provide better knowledge about the specific disciplines favored by government interest.


The following appendices are part of this document. Click on the hyperlinks to view the documents,
Appendix A: Matrix of the results for all patents containing Government Interest fields. The thirteen most cited classifications for each year are listed.
Appendix B: Java code used to obtain the classifications in patents with a Government Interest field.
Appendix C: Scatter graph of most cited classifications.
Appendix D: Scatter graph of citation frequency per classification.